Fix pickle cache rewrite races

[shaypal5]

Summary

• make shared pickle-cache rewrites atomic with a temp file plus os.replace
• use a sidecar lockfile outside cache directories for shared pickle-cache reads and writes so Windows can replace cache files safely
• handle moved filesystem events in the pickle watchdog path
• add regression coverage for concurrent shared-cache rewrites

Context

• fixes the macOS cleanup failure in tests/test_cleanup.py::test_cleanup_stale_entries
• fixes the Windows smoke-test regression from replacing an open cache file
• preserves expected cache-directory contents for separate_files=True and separate_files=False

Files

• src/cachier/cores/pickle.py
• tests/pickle_tests/test_pickle_core.py

[Copilot]

Pull request overview

Bumps the Cachier package version to 4.3.0 for the v4.3.0 release.

Changes:

• Updated the version string from 4.2.0 to 4.3.0

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

[shaypal5]

@Borda please review (and ignore the tiny coverage gap - it seems to be a tiny bug, since 0 missing lines show up in the report).

[Borda]

LGTM, just would think about grouping similar test to a class so the particular tests names could be shorter...

[shaypal5]

LGTM, just would think about grouping similar test to a class so the particular tests names could be shorter...

Might be worth a chore issue, if you want to open one.