Add cross-package dependency verification to CI (Dispatch #68)

[JnyJny]

Summary

Implements cross-package dependency verification for the busylight monorepo to prevent it from silently devolving into a monolith by catching undeclared cross-package dependencies.

Changes

New Script: scripts/verify-cross-package-deps.py

• Scans all workspace members for cross-package imports
• Cross-references imports against declared dependencies in pyproject.toml
• Fails the build on any undeclared cross-package imports
• Uses Python AST parsing for accurate import detection
• Handles relative imports and module name mapping correctly

CI Integration

• Added dependency verification step to .github/workflows/ci.yml
• Runs as part of the dependency-check job
• Provides clear error messages and remediation guidance

Documentation

• Added scripts/README.md explaining the verification process
• Documented relationship to existing deptry checks

Technical Details

• AST Parsing: Uses Python's ast module to accurately parse import statements
• Relative Import Handling: Correctly ignores relative imports (e.g., from .module import ...)
• Dependency Mapping: Handles both package names (busylight-core) and module names (busylight_core)
• Workspace Detection: Automatically discovers packages via uv workspace configuration

Testing

The script correctly identifies the current valid cross-package dependency:

• busylight-for-humans → busylight_core (properly declared as busylight-core>=2.3.0)

Dispatch #68

This addresses the requirement to "Add prek dependency verification to busylight-core monorepo CI" by implementing a custom solution that:

1. ✅ Scans all imports in each workspace member
2. ✅ Cross-references against declared dependencies in pyproject.toml
3. ✅ Fails the build on undeclared cross-package imports
4. ✅ Prevents monorepo from becoming a monolith

The tool provides better monorepo-specific dependency verification than generic tools, focusing specifically on cross-package boundaries within the workspace.