feat: add one-command installation for Mac/Linux and Windows

CLAUDE.md

@@ -6,7 +6,9 @@ Autonomous coding loop for Claude Code. PRD-based workflow with bash implementat
 
 | Use Case                 | Command                                                                                        |
 | ------------------------ | ---------------------------------------------------------------------------------------------- |
-| **Install ralph-cli**    | `git clone https://github.com/AskTinNguyen/ralph-cli.git && cd ralph-cli && npm i && npm link` |
+| **Install (Mac/Linux)**  | `curl -fsSL https://raw.githubusercontent.com/AskTinNguyen/ralph-cli/main/install.sh \| bash`  |
+| **Install (Windows)**    | `iwr -useb https://raw.githubusercontent.com/AskTinNguyen/ralph-cli/main/install.ps1 \| iex`   |
+| **Install (manual)**     | `git clone https://github.com/AskTinNguyen/ralph-cli.git && cd ralph-cli && npm i && npm link` |
 | **Install to project**   | `ralph install`                                                                                |
 | **Generate PRD**         | `ralph prd`                                                                                    |
 | **Create plan from PRD** | `ralph plan` (creates PRD-N folder)                                                            |

README.md

@@ -6,13 +6,30 @@ Ralph is a minimal, file-based agent loop for autonomous coding. Each iteration
 
 ## Quick Start (5 minutes)
 
-### Prerequisites
+### One-Command Install
+
+**macOS / Linux:**
+```bash
+curl -fsSL https://raw.githubusercontent.com/AskTinNguyen/ralph-cli/main/install.sh | bash
+```
+
+**Windows (PowerShell):**
+```powershell
+iwr -useb https://raw.githubusercontent.com/AskTinNguyen/ralph-cli/main/install.ps1 | iex
+```
+
+The installer automatically:
+- Checks for Node.js (v18+), npm, and Git
+- Installs missing dependencies (via Homebrew, apt, winget, or Chocolatey)
+- Clones and sets up ralph-cli globally
+
+### Prerequisites (if installing manually)
 
 - Node.js 18+
 - Git
 - An AI agent: [Claude Code](https://claude.ai/download), [Codex](https://github.com/openai/codex), or [Droid](https://factory.ai)
 
-### Install Ralph
+### Manual Install
 
 ```bash
 git clone https://github.com/AskTinNguyen/ralph-cli.git
@@ -45,7 +62,24 @@ Ralph treats **files and git** as memory, not the model context:
 
 ## Installation
 
-### From GitHub (Recommended)
+### One-Command Install (Recommended)
+
+**macOS / Linux:**
+```bash
+curl -fsSL https://raw.githubusercontent.com/AskTinNguyen/ralph-cli/main/install.sh | bash
+```
+
+**Windows (PowerShell):**
+```powershell
+iwr -useb https://raw.githubusercontent.com/AskTinNguyen/ralph-cli/main/install.ps1 | iex
+```
+
+**Custom install directory:**
+```bash
+RALPH_INSTALL_DIR=/opt/ralph curl -fsSL https://raw.githubusercontent.com/AskTinNguyen/ralph-cli/main/install.sh | bash
+```
+
+### From GitHub (Manual)
 
 ```bash
 git clone https://github.com/AskTinNguyen/ralph-cli.git