diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
new file mode 100644
index 0000000..0f93456
--- /dev/null
+++ b/.github/workflows/check.yml
@@ -0,0 +1,38 @@
+name: Check
+
+on:
+  pull_request:
+
+jobs:
+  test:
+    strategy:
+      fail-fast: false
+      matrix:
+        runner:
+          - ubuntu-22.04
+          - macos-latest
+    runs-on: ${{ matrix.runner }}
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install system dependencies (Linux)
+        if: runner.os == 'Linux'
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y \
+            libwebkit2gtk-4.1-dev \
+            libgtk-3-dev \
+            libappindicator3-dev \
+            librsvg2-dev \
+            patchelf \
+            xdg-utils
+
+      - name: Install Rust
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Stub frontendDist for cargo build
+        run: mkdir -p dist
+
+      - name: Run cargo test
+        working-directory: src-tauri
+        run: cargo test
\ No newline at end of file
diff --git a/CHANGELOG.md b/CHANGELOG.md
index adcfba2..e2b7207 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 ## [Unreleased]
 
 ### Added
+- Native menu bar (File / Edit / View / Window / Help) with platform-gated accelerators
+- Markdown file associations (`.md` / `.markdown` / `.mdx`) so Marky can be the default viewer
+- PR check running `cargo test` on macOS and Linux
 - Adjustable text size — scales all text app-wide (sidebar, toolbar, command palette, markdown content) via Settings dropdown or Cmd+Plus/Cmd+Minus/Cmd+0
 - Resizable sidebars — drag the edge of the folder sidebar or table of contents to resize; double-click to reset to default
 - Copy contents as markdown
diff --git a/src-tauri/src/lib.rs b/src-tauri/src/lib.rs
index 244ce1b..1cf52c0 100644
--- a/src-tauri/src/lib.rs
+++ b/src-tauri/src/lib.rs
@@ -3,6 +3,7 @@ mod commands;
 mod error;
 mod folder;
 mod fs;
+mod menu;
 mod registry;
 mod search;
 mod settings;
@@ -110,8 +111,14 @@ pub fn run() {
             app.manage(InitialTargetState(Mutex::new(initial_resolved)));
             app.manage(registry);
             app.manage(watchers);
+
+            let (menu, handles) = menu::build(app.handle())?;
+            app.set_menu(menu)?;
+            app.manage(handles);
+
             Ok(())
         })
+        .on_menu_event(menu::handle_event)
         .invoke_handler(tauri::generate_handler![
             commands::get_initial_target,
             commands::set_initial_target,
diff --git a/src-tauri/src/menu.rs b/src-tauri/src/menu.rs
new file mode 100644
index 0000000..64b1a43
--- /dev/null
+++ b/src-tauri/src/menu.rs
@@ -0,0 +1,371 @@
+//! Native menu bar: static menu construction, id parsing, and event routing.
+//!
+//! Platform differences (see docs/plans/native-menu-bar.md "Platform gating")
+//! live entirely in this module via `#[cfg(target_os = "macos")]` /
+//! `#[cfg(not(target_os = "macos"))]`. `cfg!()` is only used for label text.
+
+use tauri::menu::{
+    Menu, MenuBuilder, MenuEvent, MenuItem, MenuItemBuilder, Submenu, SubmenuBuilder,
+};
+use tauri::{AppHandle, Emitter, Manager, Wry};
+use tauri_plugin_opener::OpenerExt;
+
+/// Menu items whose enabled state depends on app state (has-file /
+/// has-folder). Stored in Tauri managed state so a later task (#004) can
+/// toggle them without rebuilding the whole menu. The recent-files/folders
+/// submenus are populated by #003.
+pub struct MenuHandles {
+    #[allow(dead_code)]
+    pub file_items: Vec<MenuItem<Wry>>,
+    #[allow(dead_code)]
+    pub folder_items: Vec<MenuItem<Wry>>,
+    #[allow(dead_code)]
+    pub recent_files: Submenu<Wry>,
+    #[allow(dead_code)]
+    pub recent_folders: Submenu<Wry>,
+}
+
+/// Build the full native menu bar (app, File, Edit, View, Window, Help).
+pub fn build(app: &AppHandle) -> tauri::Result<(Menu<Wry>, MenuHandles)> {
+    let mut builder = MenuBuilder::new(app);
+
+    #[cfg(target_os = "macos")]
+    {
+        builder = builder.item(&app_menu(app)?);
+    }
+
+    let (file_menu, file_items, folder_items, recent_files, recent_folders) = file_menu(app)?;
+    builder = builder.item(&file_menu).item(&edit_menu(app)?).item(&view_menu(app)?);
+
+    #[cfg(target_os = "macos")]
+    {
+        builder = builder.item(&window_menu(app)?);
+    }
+
+    builder = builder.item(&help_menu(app)?);
+
+    let menu = builder.build()?;
+
+    Ok((
+        menu,
+        MenuHandles {
+            file_items,
+            folder_items,
+            recent_files,
+            recent_folders,
+        },
+    ))
+}
+
+#[cfg(target_os = "macos")]
+fn app_menu(app: &AppHandle) -> tauri::Result<Submenu<Wry>> {
+    SubmenuBuilder::new(app, "Marky")
+        .about_with_text("About Marky", None)
+        .separator()
+        .services()
+        .separator()
+        .hide_with_text("Hide Marky")
+        .hide_others()
+        .show_all()
+        .separator()
+        .quit_with_text("Quit Marky")
+        .build()
+}
+
+type FileMenuParts = (
+    Submenu<Wry>,
+    Vec<MenuItem<Wry>>,
+    Vec<MenuItem<Wry>>,
+    Submenu<Wry>,
+    Submenu<Wry>,
+);
+
+fn file_menu(app: &AppHandle) -> tauri::Result<FileMenuParts> {
+    let open = MenuItemBuilder::with_id("open", "Open…")
+        .accelerator("CmdOrCtrl+O")
+        .build(app)?;
+    let open_folder = MenuItemBuilder::with_id("open-folder", "Open Folder…")
+        .accelerator("CmdOrCtrl+Shift+O")
+        .build(app)?;
+
+    // Populated by #003; empty and disabled for now.
+    let recent_files = SubmenuBuilder::with_id(app, "recent-files", "Open Recent")
+        .enabled(false)
+        .build()?;
+    let recent_folders = SubmenuBuilder::with_id(app, "recent-folders", "Open Recent Folder")
+        .enabled(false)
+        .build()?;
+
+    let reload_file = MenuItemBuilder::with_id("reload-file", "Reload File")
+        .accelerator("CmdOrCtrl+R")
+        .build(app)?;
+    let rescan_folder = MenuItemBuilder::with_id("rescan-folder", "Rescan Folder")
+        .accelerator("CmdOrCtrl+Shift+R")
+        .build(app)?;
+
+    let export_html = MenuItemBuilder::with_id("export-html", "HTML…")
+        .accelerator("Alt+CmdOrCtrl+E")
+        .build(app)?;
+    let export_markdown = MenuItemBuilder::with_id("export-markdown", "Markdown Copy…")
+        .accelerator("CmdOrCtrl+Shift+S")
+        .build(app)?;
+    let export_menu = SubmenuBuilder::new(app, "Export")
+        .item(&export_html)
+        .item(&export_markdown)
+        .build()?;
+
+    let print = MenuItemBuilder::with_id("print", "Print…")
+        .accelerator("CmdOrCtrl+P")
+        .build(app)?;
+
+    let reveal_label = if cfg!(target_os = "macos") {
+        "Reveal in Finder"
+    } else {
+        "Show in File Manager"
+    };
+    let reveal = MenuItemBuilder::with_id("reveal", reveal_label)
+        .accelerator("Alt+CmdOrCtrl+R")
+        .build(app)?;
+
+    let close_tab = MenuItemBuilder::with_id("close-tab", "Close Tab")
+        .accelerator("CmdOrCtrl+W")
+        .build(app)?;
+    let close_folder = MenuItemBuilder::with_id("close-folder", "Close Folder")
+        .accelerator("CmdOrCtrl+Shift+W")
+        .build(app)?;
+
+    let builder = SubmenuBuilder::new(app, "File")
+        .item(&open)
+        .item(&open_folder)
+        .item(&recent_files)
+        .item(&recent_folders)
+        .separator()
+        .item(&reload_file)
+        .item(&rescan_folder)
+        .separator()
+        .item(&export_menu)
+        .item(&print)
+        .separator()
+        .item(&reveal);
+
+    #[cfg(target_os = "macos")]
+    let open_with = MenuItemBuilder::with_id("open-with", "Open With…")
+        .accelerator("Alt+CmdOrCtrl+O")
+        .build(app)?;
+    #[cfg(target_os = "macos")]
+    let builder = builder.item(&open_with);
+
+    let builder = builder.separator().item(&close_tab).item(&close_folder);
+
+    #[cfg(not(target_os = "macos"))]
+    let quit = MenuItemBuilder::with_id("quit", "Quit")
+        .accelerator("Ctrl+Q")
+        .build(app)?;
+    #[cfg(not(target_os = "macos"))]
+    let builder = builder.separator().item(&quit);
+
+    let file_menu = builder.build()?;
+
+    let mut file_items = vec![
+        reload_file,
+        export_html,
+        export_markdown,
+        print,
+        reveal,
+        close_tab,
+    ];
+    #[cfg(target_os = "macos")]
+    file_items.push(open_with);
+
+    let folder_items = vec![rescan_folder, close_folder];
+
+    Ok((
+        file_menu,
+        file_items,
+        folder_items,
+        recent_files,
+        recent_folders,
+    ))
+}
+
+fn edit_menu(app: &AppHandle) -> tauri::Result<Submenu<Wry>> {
+    let builder = SubmenuBuilder::new(app, "Edit");
+
+    #[cfg(target_os = "macos")]
+    let builder = builder.undo().redo().separator();
+
+    let find = MenuItemBuilder::with_id("find", "Find…")
+        .accelerator("CmdOrCtrl+F")
+        .build(app)?;
+
+    builder
+        .cut()
+        .copy()
+        .paste()
+        .select_all()
+        .separator()
+        .item(&find)
+        .build()
+}
+
+fn view_menu(app: &AppHandle) -> tauri::Result<Submenu<Wry>> {
+    let command_palette = MenuItemBuilder::with_id("command-palette", "Command Palette")
+        .accelerator("CmdOrCtrl+K")
+        .build(app)?;
+    let split_right = MenuItemBuilder::with_id("split-right", "Split Right")
+        .accelerator("CmdOrCtrl+\\")
+        .build(app)?;
+    let split_down = MenuItemBuilder::with_id("split-down", "Split Down")
+        .accelerator("CmdOrCtrl+Shift+\\")
+        .build(app)?;
+    let close_split = MenuItemBuilder::with_id("close-split", "Close Split").build(app)?;
+    let zoom_reset = MenuItemBuilder::with_id("zoom-reset", "Actual Size")
+        .accelerator("CmdOrCtrl+0")
+        .build(app)?;
+    let zoom_in = MenuItemBuilder::with_id("zoom-in", "Zoom In")
+        .accelerator("CmdOrCtrl+=")
+        .build(app)?;
+    let zoom_out = MenuItemBuilder::with_id("zoom-out", "Zoom Out")
+        .accelerator("CmdOrCtrl+-")
+        .build(app)?;
+
+    let builder = SubmenuBuilder::new(app, "View")
+        .item(&command_palette)
+        .separator()
+        .item(&split_right)
+        .item(&split_down)
+        .item(&close_split)
+        .separator()
+        .item(&zoom_reset)
+        .item(&zoom_in)
+        .item(&zoom_out)
+        .separator();
+
+    #[cfg(target_os = "macos")]
+    let builder = builder.fullscreen_with_text("Enter Full Screen");
+
+    #[cfg(not(target_os = "macos"))]
+    let builder = {
+        let toggle_fullscreen = MenuItemBuilder::with_id("toggle-fullscreen", "Toggle Full Screen")
+            .accelerator("F11")
+            .build(app)?;
+        builder.item(&toggle_fullscreen)
+    };
+
+    builder.build()
+}
+
+#[cfg(target_os = "macos")]
+fn window_menu(app: &AppHandle) -> tauri::Result<Submenu<Wry>> {
+    let submenu = SubmenuBuilder::new(app, "Window")
+        .minimize()
+        .maximize_with_text("Zoom")
+        .build()?;
+    // Makes AppKit add "Bring All to Front" plus the window list for us.
+    submenu.set_as_windows_menu_for_nsapp()?;
+    Ok(submenu)
+}
+
+fn help_menu(app: &AppHandle) -> tauri::Result<Submenu<Wry>> {
+    let help_github = MenuItemBuilder::with_id("help-github", "Marky on GitHub").build(app)?;
+    let help_issue = MenuItemBuilder::with_id("help-issue", "Report an Issue").build(app)?;
+
+    let builder = SubmenuBuilder::new(app, "Help");
+
+    #[cfg(not(target_os = "macos"))]
+    let builder = builder.about_with_text("About Marky", None).separator();
+
+    let submenu = builder.item(&help_github).item(&help_issue).build()?;
+
+    #[cfg(target_os = "macos")]
+    submenu.set_as_help_menu_for_nsapp()?;
+
+    Ok(submenu)
+}
+
+/// Parsed intent of a menu id. Most ids are simply forwarded to the frontend
+/// as `menu://action`; a handful are handled entirely in Rust.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum MenuCommand {
+    OpenUrl(&'static str),
+    Quit,
+    ToggleFullscreen,
+    Forward(String),
+}
+
+/// Pure mapping from a menu item id to the command it represents. Kept free
+/// of side effects so it's easy to unit test.
+pub fn parse_menu_id(id: &str) -> MenuCommand {
+    match id {
+        "help-github" => MenuCommand::OpenUrl("https://github.com/GRVYDEV/marky"),
+        "help-issue" => MenuCommand::OpenUrl("https://github.com/GRVYDEV/marky/issues/new"),
+        "quit" => MenuCommand::Quit,
+        "toggle-fullscreen" => MenuCommand::ToggleFullscreen,
+        other => MenuCommand::Forward(other.to_string()),
+    }
+}
+
+/// Route a native menu click. Ids not handled here are forwarded to the
+/// frontend on `menu://action` for `App.tsx` to dispatch.
+pub fn handle_event(app: &AppHandle, event: MenuEvent) {
+    match parse_menu_id(event.id().as_ref()) {
+        MenuCommand::OpenUrl(url) => {
+            if let Err(err) = app.opener().open_url(url, None::<&str>) {
+                eprintln!("menu: failed to open {url}: {err}");
+            }
+        }
+        MenuCommand::Quit => app.exit(0),
+        MenuCommand::ToggleFullscreen => {
+            if let Some(window) = app.get_webview_window("main") {
+                if let Ok(is_fullscreen) = window.is_fullscreen() {
+                    let _ = window.set_fullscreen(!is_fullscreen);
+                }
+            }
+        }
+        MenuCommand::Forward(id) => {
+            let _ = app.emit("menu://action", id);
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parses_help_github() {
+        assert_eq!(
+            parse_menu_id("help-github"),
+            MenuCommand::OpenUrl("https://github.com/GRVYDEV/marky")
+        );
+    }
+
+    #[test]
+    fn parses_help_issue() {
+        assert_eq!(
+            parse_menu_id("help-issue"),
+            MenuCommand::OpenUrl("https://github.com/GRVYDEV/marky/issues/new")
+        );
+    }
+
+    #[test]
+    fn parses_quit() {
+        assert_eq!(parse_menu_id("quit"), MenuCommand::Quit);
+    }
+
+    #[test]
+    fn parses_toggle_fullscreen() {
+        assert_eq!(
+            parse_menu_id("toggle-fullscreen"),
+            MenuCommand::ToggleFullscreen
+        );
+    }
+
+    #[test]
+    fn forwards_unrecognized_ids() {
+        assert_eq!(
+            parse_menu_id("close-tab"),
+            MenuCommand::Forward("close-tab".to_string())
+        );
+    }
+}
diff --git a/src-tauri/tauri.conf.json b/src-tauri/tauri.conf.json
index ff5d4e8..12ae127 100644
--- a/src-tauri/tauri.conf.json
+++ b/src-tauri/tauri.conf.json
@@ -34,6 +34,15 @@
       "icons/128x128@2x.png",
       "icons/icon.icns",
       "icons/icon.ico"
+    ],
+    "fileAssociations": [
+      {
+        "ext": ["md", "markdown", "mdx"],
+        "name": "Markdown Document",
+        "role": "Viewer",
+        "mimeType": "text/markdown",
+        "contentTypes": ["net.daringfireball.markdown"]
+      }
     ]
   }
 }
diff --git a/src/App.tsx b/src/App.tsx
index 6f4160c..249cf9b 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -10,7 +10,16 @@ import { Pane } from "@/components/Pane";
 import { TableOfContents } from "@/components/TableOfContents";
 import { Toolbar } from "@/components/Toolbar";
 import { CommandPalette } from "@/components/CommandPalette";
-import { tauri, onCliTarget, onFolderChanged, onFileChanged, type AnnotatedFolder } from "@/lib/tauri";
+import {
+  tauri,
+  onCliTarget,
+  onFolderChanged,
+  onFileChanged,
+  onMenuAction,
+  type AnnotatedFolder,
+  type MenuAction,
+} from "@/lib/tauri";
+import { pickAndAddFolder } from "@/lib/folders";
 import {
   createInitialState,
   reduce,
@@ -140,42 +149,6 @@ function AppShell() {
     return pathToFolderId[p] ?? null;
   }
 
-  // Global keyboard shortcuts.
-  useEffect(() => {
-    const onKey = (e: KeyboardEvent) => {
-      const meta = e.metaKey || e.ctrlKey;
-      const k = e.key.toLowerCase();
-      if (meta && k === "k") {
-        e.preventDefault();
-        setPaletteOpen((v) => !v);
-      } else if (meta && k === "o") {
-        e.preventDefault();
-        handlePickFile();
-      } else if (meta && k === "f") {
-        e.preventDefault();
-        setSearchPaneId(state.activePaneId);
-      } else if (meta && e.key === "\\") {
-        e.preventDefault();
-        dispatch({ type: "SPLIT", direction: e.shiftKey ? "horizontal" : "vertical" });
-      } else if (meta && k === "w") {
-        e.preventDefault();
-        const tabId = activePane.activeTabId;
-        if (tabId) dispatch({ type: "CLOSE_TAB", tabId, paneId: activePane.id });
-      } else if (meta && (e.key === "=" || e.key === "+")) {
-        e.preventDefault();
-        zoomIn();
-      } else if (meta && e.key === "-") {
-        e.preventDefault();
-        zoomOut();
-      } else if (meta && k === "0") {
-        e.preventDefault();
-        zoomReset();
-      }
-    };
-    window.addEventListener("keydown", onKey);
-    return () => window.removeEventListener("keydown", onKey);
-  }, [state.activePaneId, activePane.activeTabId, activePane.id, zoomIn, zoomOut, zoomReset]);
-
   // File drop opens as new tab.
   useEffect(() => {
     let unlisten: (() => void) | undefined;
@@ -206,6 +179,82 @@ function AppShell() {
       ?.scrollIntoView({ block: "start" });
   };
 
+  // Route native menu actions. Kept in a ref (updated every render) so the
+  // listener below is registered exactly once and never sees stale state.
+  const menuHandlerRef = useRef<(action: MenuAction) => void>(() => {});
+  menuHandlerRef.current = async (action: MenuAction) => {
+    switch (action) {
+      case "open":
+        handlePickFile();
+        break;
+      case "open-folder": {
+        const folder = await pickAndAddFolder();
+        if (folder) refreshFolders();
+        break;
+      }
+      case "reload-file": {
+        if (activeTab?.filePath) {
+          try {
+            const text = await tauri.readFile(activeTab.filePath);
+            dispatch({ type: "UPDATE_TAB_SOURCE", tabId: activeTab.id, source: text });
+          } catch (err) {
+            console.error("failed to reload file", err);
+          }
+        }
+        break;
+      }
+      case "close-tab": {
+        const tabId = activePane.activeTabId;
+        if (tabId) dispatch({ type: "CLOSE_TAB", tabId, paneId: activePane.id });
+        break;
+      }
+      case "find":
+        setSearchPaneId(state.activePaneId);
+        break;
+      case "command-palette":
+        setPaletteOpen((v) => !v);
+        break;
+      case "split-right":
+        dispatch({ type: "SPLIT", direction: "vertical" });
+        break;
+      case "split-down":
+        dispatch({ type: "SPLIT", direction: "horizontal" });
+        break;
+      case "close-split":
+        handleCloseSplit();
+        break;
+      case "zoom-in":
+        zoomIn();
+        break;
+      case "zoom-out":
+        zoomOut();
+        break;
+      case "zoom-reset":
+        zoomReset();
+        break;
+      case "rescan-folder":
+      case "close-folder":
+        // TODO(#002)
+        break;
+      case "print":
+      case "reveal":
+      case "open-with":
+        // TODO(#005)
+        break;
+      case "export-html":
+      case "export-markdown":
+        // TODO(#006)
+        break;
+    }
+  };
+
+  useEffect(() => {
+    const off = onMenuAction((action) => menuHandlerRef.current(action));
+    return () => {
+      off.then((fn) => fn());
+    };
+  }, []);
+
   const renderPane = (paneId: string) => {
     const pane = state.panes.find((p) => p.id === paneId)!;
     return (
diff --git a/src/components/FolderSidebar.tsx b/src/components/FolderSidebar.tsx
index ee2a500..1785005 100644
--- a/src/components/FolderSidebar.tsx
+++ b/src/components/FolderSidebar.tsx
@@ -1,6 +1,6 @@
 import { useEffect, useState, useCallback } from "react";
-import { open as openDialog } from "@tauri-apps/plugin-dialog";
 import { tauri, onFolderChanged, type AnnotatedFolder, type TreeNode } from "@/lib/tauri";
+import { pickAndAddFolder } from "@/lib/folders";
 import { usePreferences } from "@/lib/preferences";
 import { Button } from "@/components/ui/button";
 import { ScrollArea } from "@/components/ui/scroll-area";
@@ -92,11 +92,8 @@ export function FolderSidebar({ activePath, onOpenFile, onOpenPalette, refreshNo
   }, []);
 
   const handleAdd = async () => {
-    const picked = await openDialog({ directory: true, multiple: false });
-    if (typeof picked === "string") {
-      await tauri.addFolder(picked);
-      await loadAll();
-    }
+    const folder = await pickAndAddFolder();
+    if (folder) await loadAll();
   };
 
   const handleRemove = async (id: string) => {
diff --git a/src/lib/folders.ts b/src/lib/folders.ts
new file mode 100644
index 0000000..a3f7a63
--- /dev/null
+++ b/src/lib/folders.ts
@@ -0,0 +1,13 @@
+import { open as openDialog } from "@tauri-apps/plugin-dialog";
+import { tauri, type Folder } from "@/lib/tauri";
+
+/**
+ * Open the native "choose a folder" dialog and, if the user picks one,
+ * register it with the backend. Shared by the sidebar's + button and the
+ * File ▸ Open Folder… menu action so both go through one code path.
+ */
+export async function pickAndAddFolder(): Promise<Folder | null> {
+  const picked = await openDialog({ directory: true, multiple: false });
+  if (typeof picked !== "string") return null;
+  return tauri.addFolder(picked);
+}
diff --git a/src/lib/tauri.ts b/src/lib/tauri.ts
index c5993c7..05cde9f 100644
--- a/src/lib/tauri.ts
+++ b/src/lib/tauri.ts
@@ -73,3 +73,28 @@ export function onFileChanged(cb: (paths: string[]) => void): Promise<UnlistenFn
 export function onCliTarget(cb: (t: InitialTarget) => void): Promise<UnlistenFn> {
   return listen<InitialTarget>("cli://target", (e) => cb(e.payload));
 }
+
+export type MenuAction =
+  | "open"
+  | "open-folder"
+  | "reload-file"
+  | "rescan-folder"
+  | "export-html"
+  | "export-markdown"
+  | "print"
+  | "reveal"
+  | "open-with"
+  | "close-tab"
+  | "close-folder"
+  | "find"
+  | "command-palette"
+  | "split-right"
+  | "split-down"
+  | "close-split"
+  | "zoom-in"
+  | "zoom-out"
+  | "zoom-reset";
+
+export function onMenuAction(cb: (action: MenuAction) => void): Promise<UnlistenFn> {
+  return listen<MenuAction>("menu://action", (e) => cb(e.payload));
+}
diff --git a/src/styles/markdown.css b/src/styles/markdown.css
index 807bbdb..8273c94 100644
--- a/src/styles/markdown.css
+++ b/src/styles/markdown.css
@@ -3,13 +3,19 @@
 .markdown-body {
   @apply text-foreground leading-7;
   font-size: 0.9375rem;
-  max-width: 860px;
+  width: 100%;
+  max-width: none;
+  box-sizing: border-box;
   margin: 0 auto;
   padding: 2rem 2.5rem 6rem;
 }
 
-.markdown-body > *:first-child { margin-top: 0; }
-.markdown-body > *:last-child { margin-bottom: 0; }
+.markdown-body > *:first-child {
+  margin-top: 0;
+}
+.markdown-body > *:last-child {
+  margin-bottom: 0;
+}
 
 .markdown-body h1,
 .markdown-body h2,
@@ -22,32 +28,76 @@
   margin-bottom: 0.75rem;
   scroll-margin-top: 4rem;
 }
-.markdown-body h1 { font-size: 2rem; line-height: 1.2; border-bottom: 1px solid var(--border); padding-bottom: 0.4em; }
-.markdown-body h2 { font-size: 1.5rem; line-height: 1.3; border-bottom: 1px solid var(--border); padding-bottom: 0.3em; }
-.markdown-body h3 { font-size: 1.25rem; }
-.markdown-body h4 { font-size: 1.05rem; }
-.markdown-body h5 { font-size: 0.95rem; @apply text-muted-foreground; }
-.markdown-body h6 { font-size: 0.85rem; @apply text-muted-foreground uppercase tracking-wider; }
+.markdown-body h1 {
+  font-size: 2rem;
+  line-height: 1.2;
+  border-bottom: 1px solid var(--border);
+  padding-bottom: 0.4em;
+}
+.markdown-body h2 {
+  font-size: 1.5rem;
+  line-height: 1.3;
+  border-bottom: 1px solid var(--border);
+  padding-bottom: 0.3em;
+}
+.markdown-body h3 {
+  font-size: 1.25rem;
+}
+.markdown-body h4 {
+  font-size: 1.05rem;
+}
+.markdown-body h5 {
+  font-size: 0.95rem;
+  @apply text-muted-foreground;
+}
+.markdown-body h6 {
+  font-size: 0.85rem;
+  @apply text-muted-foreground uppercase tracking-wider;
+}
 
-.markdown-body p { margin: 0.75rem 0; }
-.markdown-body a { @apply text-primary underline underline-offset-2; }
-.markdown-body a:hover { @apply opacity-80; }
+.markdown-body p {
+  margin: 0.75rem 0;
+}
+.markdown-body a {
+  @apply text-primary underline underline-offset-2;
+}
+.markdown-body a:hover {
+  @apply opacity-80;
+}
 
-.markdown-body strong { @apply font-semibold; }
-.markdown-body em { font-style: italic; }
-.markdown-body del { @apply text-muted-foreground line-through; }
+.markdown-body strong {
+  @apply font-semibold;
+}
+.markdown-body em {
+  font-style: italic;
+}
+.markdown-body del {
+  @apply text-muted-foreground line-through;
+}
 
 .markdown-body ul,
 .markdown-body ol {
   margin: 0.75rem 0;
   padding-left: 1.5rem;
 }
-.markdown-body ul { list-style: disc; }
-.markdown-body ol { list-style: decimal; }
-.markdown-body li { margin: 0.25rem 0; }
-.markdown-body li > ul, .markdown-body li > ol { margin: 0.25rem 0; }
+.markdown-body ul {
+  list-style: disc;
+}
+.markdown-body ol {
+  list-style: decimal;
+}
+.markdown-body li {
+  margin: 0.25rem 0;
+}
+.markdown-body li > ul,
+.markdown-body li > ol {
+  margin: 0.25rem 0;
+}
 
-.markdown-body .task-list-item { list-style: none; margin-left: -1.25rem; }
+.markdown-body .task-list-item {
+  list-style: none;
+  margin-left: -1.25rem;
+}
 .markdown-body .task-list-item input[type="checkbox"] {
   margin-right: 0.5rem;
   vertical-align: middle;
@@ -75,17 +125,23 @@
   display: block;
   overflow-x: auto;
 }
-.markdown-body th, .markdown-body td {
+.markdown-body th,
+.markdown-body td {
   border: 1px solid var(--border);
   padding: 0.5rem 0.75rem;
   text-align: left;
 }
-.markdown-body th { @apply bg-muted font-semibold; }
-.markdown-body tr:nth-child(2n) td { background: color-mix(in oklch, var(--muted) 40%, transparent); }
+.markdown-body th {
+  @apply bg-muted font-semibold;
+}
+.markdown-body tr:nth-child(2n) td {
+  background: color-mix(in oklch, var(--muted) 40%, transparent);
+}
 
 .markdown-body code:not(pre code) {
   @apply bg-muted text-foreground rounded;
-  font-family: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
+  font-family:
+    ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
   font-size: 0.88em;
   padding: 0.12em 0.35em;
 }
@@ -102,7 +158,8 @@
 .markdown-body pre.shiki {
   display: block;
   padding: 1rem 1.1rem;
-  font-family: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
+  font-family:
+    ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
   font-size: 0.86em;
   line-height: 1.55;
   overflow-x: auto;
@@ -111,8 +168,13 @@
 /* Shiki paints inline color/background on the <pre> and on every token
    <span> based on the theme passed at render time, so no extra mapping
    needed here. We just keep padding consistent with our own pre rule. */
-.markdown-body pre.shiki { padding: 1rem 1.1rem; }
-.markdown-body pre.shiki code { background: transparent; padding: 0; }
+.markdown-body pre.shiki {
+  padding: 1rem 1.1rem;
+}
+.markdown-body pre.shiki code {
+  background: transparent;
+  padding: 0;
+}
 
 .markdown-body .copy-code-btn {
   position: absolute;
@@ -128,10 +190,17 @@
   opacity: 0;
   transition: opacity 120ms ease;
 }
-.markdown-body pre:hover .copy-code-btn { opacity: 1; }
-.markdown-body .copy-code-btn:hover { color: var(--foreground); }
+.markdown-body pre:hover .copy-code-btn {
+  opacity: 1;
+}
+.markdown-body .copy-code-btn:hover {
+  color: var(--foreground);
+}
 
-.markdown-body img { max-width: 100%; border-radius: 0.4rem; }
+.markdown-body img {
+  max-width: 100%;
+  border-radius: 0.4rem;
+}
 
 .markdown-body .mermaid-block {
   background: var(--muted);
@@ -142,7 +211,10 @@
   text-align: center;
   overflow-x: auto;
 }
-.markdown-body .mermaid-block svg { max-width: 100%; height: auto; }
+.markdown-body .mermaid-block svg {
+  max-width: 100%;
+  height: auto;
+}
 
 .markdown-body mark.doc-search-match {
   background: color-mix(in oklch, var(--muted-foreground) 35%, transparent);