docs: add CLAUDE.md for Claude Code guidance

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: fengmk2

CLAUDE.md

@@ -0,0 +1,66 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Guidelines
+
+- Do not commit changes automatically. Wait for explicit user request to commit.
+
+## Project Overview
+
+GitHub Action to set up [Vite+](https://github.com/voidzero-dev/vite-plus) (`@voidzero-dev/global`) with dependency caching support. This action installs Vite+ globally and optionally caches project dependencies based on lock file detection.
+
+## Commands
+
+```bash
+# Build (required before committing - outputs to dist/)
+vite run build
+
+# Type check
+vite run typecheck
+
+# Run tests
+vite run test
+
+# Run tests in watch mode
+vite run test:watch
+
+# Lint
+vite run lint
+vite run lint:fix
+
+# Format
+vite run fmt
+vite run fmt:check
+```
+
+**Important:** Always run `vite run build` after code changes - the `dist/index.mjs` must be committed.
+
+## Architecture
+
+This is a GitHub Action with main and post execution phases (defined in `action.yml`):
+
+- **Main phase** (`src/index.ts` → `runMain`):
+  1. Install `@voidzero-dev/global` globally via npm
+  2. Restore dependency cache if enabled
+  3. Run `vite install` if requested
+
+- **Post phase** (`src/index.ts` → `runPost`):
+  1. Save dependency cache if enabled
+
+### Key Modules
+
+- `src/inputs.ts` - Parse and validate action inputs using Zod schemas
+- `src/install-viteplus.ts` - Install vite-plus globally, handles GitHub Package Registry auth
+- `src/cache-restore.ts` / `src/cache-save.ts` - Dependency caching via `@actions/cache`
+- `src/run-install.ts` - Execute `vite install` with optional cwd/args
+- `src/types.ts` - Shared types, enums, and Zod schemas
+- `src/utils.ts` - Lock file detection, package manager cache path resolution
+
+### Lock File Detection
+
+Auto-detects package manager from lock files: `pnpm-lock.yaml`, `package-lock.json`, `yarn.lock`, `bun.lockb`
+
+## Testing
+
+Tests are colocated with source files (e.g., `src/inputs.test.ts`). Run with `npm run test`.