[gouyt13]

Summary

• Split C++ build, formatting, and clang-tidy selection so each runs only for affected paths.
• Route pyproject.toml edits to Python quality, package builds, and wheel tests without running C++ checks.
• Stop running the nonblocking include-cleaner job on every C++ change; keep its local script available.
• Update selector regression tests and maintainer documentation.

The detector and workflow files change in this PR, so the existing fail-safe selects the full CI matrix once. Subsequent changes use the narrower routing.

Verification

• python -m unittest discover -s .github/scripts -p 'test_*.py' (21 tests passed)
• python -m ruff format --check .github/scripts
• python -m ruff check .github/scripts
• RUFF=<project-environment>/bin/ruff ./scripts/check-python.sh
• Parsed all workflow YAML, checked detector output wiring and edited Markdown links
• git diff --check