feat: add comprehensive contributing documentation and streamline README

- Add CONTRIBUTING.md with detailed development setup, testing, and workflow guidelines
- Add docs/contributing.md with overview and links to detailed guide
- Remove development section from README, replace with Contributing section
- Update mkdocs.yml navigation to include contributing documentation
- Streamline README to focus on what, installation, quick start, and docs links
- Add Sphinx docstring format link for contributor reference

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

Co-Authored-By: Claude <[email protected]>

Author: JnyJny