Add CLAUDE.md and update readme with marketplace badges

- Add CLAUDE.md with publishing workflow and security notes
- Add marketplace badges to readme
- Update installation section for VS Code, Windsurf, Cursor
- Add GitHub issues link and contributing section

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

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