docs: add CLAUDE.md for Claude Code guidance

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Critical Rules
+
+**These rules override all other instructions:**
+
+1. **NEVER commit directly to main** - Always create a feature branch and submit a pull request
+2. **Conventional commits** - Format: `type(scope): description`
+3. **GitHub Issues for TODOs** - Use `gh` CLI to manage issues, no local TODO files. Use conventional commit format for issue titles
+4. **Pull Request titles** - Use conventional commit format (same as commits)
+5. **Branch naming** - Use format: `type/short-description` (e.g., `feat/settings-dialog`)
+6. **Working an issue** - Always create a new branch from an updated main branch
+7. **Check branch status before pushing** - Verify the remote tracking branch still exists. If a PR was merged/deleted, create a new branch from main instead
+
+---
+
+### GitHub CLI Commands
+
+```bash
+gh issue list                    # List open issues
+gh issue view <number>           # View details
+gh issue create --title "type(scope): description" --body "..."
+gh issue close <number>
+```
+
+### Conventional Commit Types
+
+| Type | Description |
+|------|-------------|
+| `feat` | New feature |
+| `fix` | Bug fix |
+| `docs` | Documentation only |
+| `refactor` | Code change that neither fixes a bug nor adds a feature |
+| `test` | Adding or updating tests |
+| `chore` | Maintenance tasks |
+| `perf` | Performance improvement |
+| `ci` | CI/CD changes |
+
+---
+
+## Project Overview
+
+GitHub Action to publish Visual Studio extensions to the Visual Studio Marketplace. This action only runs on Windows-based runners.
+
+## Commands
+
+```bash
+# Install dependencies
+npm ci
+
+# Run all checks (format, lint, test, package)
+npm run all
+
+# Individual commands
+npm run format:check    # Check formatting
+npm run format:write    # Fix formatting
+npm run lint            # Run ESLint
+npm run test            # Run tests
+npm run ci-test         # Run tests (CI mode)
+npm run package         # Bundle with ncc to dist/
+npm run bundle          # Format + package
+```
+
+## Architecture
+
+This is a single-file TypeScript GitHub Action:
+
+- `src/index.ts` - The entire action logic:
+  1. Validates Windows platform requirement
+  2. Resolves paths for publish manifest and VSIX file
+  3. Locates Visual Studio installation via `vswhere.exe`
+  4. Runs `VsixPublisher.exe` to publish the extension
+
+- `action.yml` - Action metadata defining inputs (`marketplace-pat`, `publish-manifest-path`, `vsix-path`, `vs-version`, `vs-prerelease`)
+- `dist/index.js` - Bundled output (committed, built with `@vercel/ncc`)
+- `__tests__/index.test.ts` - Jest tests
+
+## Key Details
+
+- Node.js 21+ required (see `.node-version`)
+- ESLint config at `.github/linters/.eslintrc.yml`
+- The bundled `dist/` directory must be committed after changes to source
+- TypeScript strict mode enabled