feat(cli): add scan --broken-refs to report unresolved block refs.

[vbhavh]

Description

Fixes: #29

Type of change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• [y] ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update

🛡️ Sovereign Developer Checklist

• [y] I have read CONTRIBUTING.md (or picked a task from docs/GOOD_FIRST_ISSUES.md).
• [y] I have executed make all locally, and all linters (Ruff), type-checkers (Mypy), and tests (Pytest) pass successfully.
• [y] I have added/updated tests for my changes (if applicable).
• [y] I have updated the relevant documentation (README.md, docs/, CONTRIBUTING.md as needed).
• [y] I updated CHANGELOG.md under [Unreleased] for user-visible behavior changes.
• [y] My code follows the project's typing conventions (explicit hints on new functions; Pydantic strict=True on domain models).

Screenshots / CLI Output (if applicable)

->expose LogseqGraph.get_broken_references() from the -->?-KINETIC scan command
->print unresolved ((uuid)) refs in a Rich table when --broken---refs is enabled
->exit with status 1 when broken refs are found
->add regression coverage in test_kinetic.py
->document the new CLI hygiene flag in CHANGELOG.md

[MarcoPorcellato]

Thanks for picking up GFI-11 / #29 — this is exactly the kind of focused CLI wiring we wanted: a small surface on scan, a clear Rich table, and an exit code that CI can rely on.

Welcome to the repo; hope to see more contributions from you. For future PRs, prefer a dedicated feature branch on your fork (rather than main) so you can keep working in parallel.

Merged via squash. Closes #29.