docs: refine README with documentation links

- Simplify introduction and add direct links to docs
- Update features with links to provider documentation
- Condense quick start while keeping CLI output examples
- Streamline installation section with link to full guide
- Simplify profiles and providers sections
- Keep essential examples with links to detailed docs
- Add CLI reference section
- Replace provider implementation details with contributing section

The README now serves as a concise overview with comprehensive
documentation links for users who need more details.

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

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

Author: domenkozar