Prevent repeated no-op project rebuilds

[LunaMeerkats]

Summary

• record a successful build's start time as the logical source-freshness cutoff
• retain the installed files' physical timestamp separately for installation-change detection
• expose reset_build_timestamp=False as an opt-out to the legacy comparison
• exclude Maturin-installed .pdb, .dwp, and .dSYM siblings from mixed-project source scans
• preserve compatibility with existing build-status cache files

Fixes #28.

Rationale

When Cargo accepts a build request but does not rewrite the extension, comparing source files only with the unchanged
extension timestamp causes the import hook to request the same no-op build indefinitely. A pre-build logical cutoff
stops that loop without hiding files modified during a build. The physical installation timestamp remains separate so
an external installation change still invalidates the cache.

Current Maturin versions also copy debug-info artifacts beside editable mixed-project extensions. Treating those
generated siblings as source would cause an unnecessary follow-up rebuild, so the searcher excludes only debug
artifacts whose names match the installed extension module.

Validation

• uvx pre-commit run --all-files
• no-op rebuild regression: 2 passed (default and explicit legacy opt-out)
• existing low-resolution timestamp regression: 1 passed
• mixed PyO3 project rebuild regression: 1 passed
• installed debug-info classification regression: 1 passed
• tests/test_import_hook/test_utilities.py: 51 passed, 1 existing skip
• python -m compileall -q src tests

The integration tests ran on CPython 3.13.13. A CPython 3.14 attempt was not applicable because the pinned PyO3 0.24.2
test dependency supports at most Python 3.13.

Provenance

The implementation, tests, and pull-request text were prepared and submitted by an autonomous OpenAI Codex agent
operating on behalf of LunaMeerkats. No human review or authorship is claimed.