Improve type precision in libregrtest excepthook, export clinic.cpp module in __all__, enhance Dependabot update frequency and rebasing, and fix test_compute_changes logic

[George-Codr]

Title: Improve type precision in libregrtest excepthook, export clinic.cpp module in all, enhance Dependabot update frequency and rebasing, and fix test_compute_changes logic

Problem / Motivation

Several developer-experience and maintenance issues exist in the current fork:

1. The type annotation for the optional excepthook argument in Lib/test/libregrtest/utils.py uses Any | None, which defeats most benefits of static type checking in that area.
2. The cpp module inside Tools/clinic/libclinic is imported and used internally but is not present in __all__, so it is not formally exported and may confuse type checkers or linters that respect __all__.
3. Dependabot is currently configured for monthly updates with no automatic rebasing strategy, which leads to delayed dependency updates and frequent manual conflict resolution during CI.
4. A small logic bug exists in the test suite file Lib/test/test_tools/test_compute_changes.py that can produce incorrect test outcomes under certain conditions.
5. Fork-specific files (CODEOWNERS, selected GitHub Actions workflows) contain minor outdated or redundant entries.

Proposed Improvements

• Replace the loose type Any | None with the exact signature Callable[[threading.ExceptHookArgs], None] | None for the excepthook parameter in libregrtest/utils.py.
• Explicitly add "cpp" to __all__ in Tools/clinic/libclinic/__init__.py (and ensure the import remains).
• Update .github/dependabot.yml:
  • Change schedule.interval from monthly → weekly
  • Add rebase-strategy: auto to reduce merge conflicts
• Apply small clean-ups to fork-specific:
  • .github/CODEOWNERS
  • Three workflow files under .github/workflows/
• Correct the conditional logic bug present in Lib/test/test_tools/test_compute_changes.py.

Scope & Impact

• All changes are strictly limited to:
  • Test suite infrastructure
  • Argument Clinic tooling
  • Static type annotations
  • Dependency update automation (Dependabot)
  • Fork-specific CI configuration
• No changes are made to:
  • Interpreter core
  • Standard library public API
  • Any compiled extension module
  • Any runtime behaviour

Checklist

• All tests pass on the three main GitHub-hosted runners (ubuntu-latest, windows-latest, macos-latest)
• mypy, pyright and pytype type checkers report no new errors
• Sourcery and CodeRabbit automated reviews applied and resolved
• Docstring coverage warning is acknowledged (planned separate improvement)

Additional context

This set of changes was developed and reviewed in PR #36 (zrsx/cpython).
All modifications aim to bring developer tooling closer to upstream CPython quality standards while keeping the fork maintainable.

Thanks in advance for any feedback or review.

[George-Codr]

#36