Add Claude Code configuration files (#272)

- Add CLAUDE.md with project overview, commands, and architecture details
- Add custom Claude commands for common workflows (commit-and-pr, fix-issue)
- Provides guidance for future Claude Code instances working with this repository

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Claude <noreply@anthropic.com>

Author: amondnet

.claude/commands/commit-and-pr.md

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+Let's commit the changes. Run tests, typechecks, and format checks. Then commit, push, and create a pull request.

.claude/commands/fix-issue.md

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+Find and fix issue #$ARGUMENTS.
+Follow these steps:
+
+1. Understand the issue described in the ticket
+2. Locate the relevant code in our codebase
+3. Implement a solution that addresses the root cause
+4. Add appropriate tests
+5. Prepare a concise PR description

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.
+
+## Project Overview
+
+This is a GitHub Action that deploys projects to Vercel. It's an npm package that integrates with GitHub workflows to automate deployments, providing more control than Vercel's native GitHub integration.
+
+## Essential Commands
+
+### Development
+```bash
+npm install              # Install dependencies
+npm start               # Run the action locally (node ./index.js)
+npm run lint            # Run ESLint on index.js
+npm run format          # Format code with Prettier
+npm run format-check    # Check code formatting
+npm test                # Run Jest tests
+npm run all             # Run format, lint, package, and test in sequence
+```
+
+### Building for Distribution
+```bash
+npm run package         # Build the action with ncc (outputs to dist/)
+```
+
+**Important**: The `dist/` folder must be committed when creating releases. This contains the bundled action code that GitHub Actions will execute.
+
+## Architecture
+
+### Core Components
+
+1. **index.js**: Main entry point that:
+   - Reads GitHub Action inputs (vercel-token, github-token, etc.)
+   - Executes Vercel CLI commands for deployment
+   - Comments on PRs/commits with deployment URLs
+   - Handles alias domain assignment
+   - Manages environment variables for Vercel org/project
+
+2. **action.yml**: Defines the GitHub Action interface:
+   - Input parameters configuration
+   - Output values (preview-url, preview-name)
+   - Runtime environment (Node.js 20)
+
+### Key Dependencies
+- `@actions/core`: GitHub Actions toolkit for inputs/outputs
+- `@actions/exec`: Execute shell commands
+- `@actions/github`: GitHub API interactions
+- `vercel`: CLI for deployments
+- `axios`: HTTP requests for alias management
+
+### Deployment Flow
+1. Action reads configuration from inputs and environment
+2. Sets up Vercel org/project IDs from `.vercel/` directory
+3. Executes `vercel` command with appropriate flags
+4. Parses deployment URL from output
+5. Optionally assigns alias domains
+6. Comments on GitHub PR/commit with deployment info
+
+## Testing Approach
+
+- Jest is configured but tests are minimal (index.test.js is empty)
+- Manual testing through example projects in `example/` directory
+- GitHub Actions workflows test different scenarios
+
+## Important Conventions
+
+1. **Vercel Configuration**: Projects must have `github.enabled: false` in vercel.json
+2. **Project Linking**: The `.vercel/` directory with org/project IDs must be committed
+3. **Build Process**: Builds should happen in GitHub Actions, not Vercel
+4. **Backward Compatibility**: Maintain support for deprecated "zeit-" prefixed inputs
+5. **Error Handling**: Use proper exit codes and clear error messages for CI/CD integration