* feat: bump vendored KiCad protos to v10.0.0
* test: add protocol contract tests for board layer name
* docs: overhaul README and guide site
- Rewrite README with punchy opening, realistic examples, and cleaner structure
- Update status to Beta and version numbers to 0.4.1
- Remove redundant sections (roadmap, future work, guide site link)
- Simplify API matrix by removing redundant Status column
- Add CONTRIBUTING.md header with welcoming message
- Expand mdBook examples with real-world patterns:
- PCB analysis (unconnected nets, footprints)
- Automation (text variables, test points)
- CI/CD integration patterns
- Net class validation
- Selection manipulation
- Update mdBook intro with comparison table and clearer goals
- Update quickstart version numbers
- Suppress missing_docs warnings for internal modules (commands, envelope, transport)
- Format code with cargo fmt
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