- Add INTEGRATION_HOWTO.md with complete treefile format specification
- Include example treefile (debian-trixie-base.yaml) for deb-bootc-compose
- Document integration patterns: CLI, Rust library, and future REST API
- Cover validation, error handling, best practices, and migration guide
- Address format mismatch between deb-bootc-compose and apt-ostree
- Provide clear documentation for external tool integration
