Add GitHub CLI authentication support

[christian-andersson]

Summary

• Add GitHub CLI (gh auth token) as an authentication fallback method
• Improves developer experience by using existing gh CLI credentials automatically
• Add local .mcp.json configuration for "dogfooding" the MCP server during development

Changes

Authentication Enhancement

• Add getGhCliToken() method in token-resolver.ts to execute gh auth token command
• Make resolveToken() async to support command execution
• Update GitHubClient to lazily resolve tokens on first request (async support)
• Add token caching to prevent repeated gh CLI calls

Authentication Resolution Order

1. Org-specific tokens (GITHUB_TOKEN_<ORG>) - for multi-org scenarios
2. Environment variable (GITHUB_TOKEN) - explicit configuration
3. GitHub CLI (gh auth token) - NEW automatic fallback
4. Unauthenticated - public repos only

Configuration Updates

• Add --allow-run=gh permission to all Deno run commands
• Update all documentation examples with the new permission
• Add .mcp.json for local development (demonstrates dogfooding)
• Remove deprecated MCP Gateway configuration from README

Documentation

• Add "With GitHub CLI" section explaining the new auth method
• Update authentication flow diagram
• Clarify when each auth method is recommended

Benefits

• Zero-config for developers: If you have gh CLI authenticated, it just works
• Better security: No need to create separate tokens for local development
• Backwards compatible: Existing token-based configurations continue to work
• Dogfooding: Project now uses its own MCP server for development

Testing

Tested with:

• Existing environment variable tokens (no regression)
• Fresh gh CLI authentication (gh auth login)
• Unauthenticated mode for public repos

🤖 Generated with Claude Code