fix(core): survive concurrent Windows log cleanup

[phernandez]

Why

• Fixes Windows: MCP server can die at startup on a log-cleanup race in _cleanup_windows_log_files #1211: concurrent Windows processes can remove a stale per-process log between discovery and timestamp sorting, allowing FileNotFoundError to escape from logging setup and terminate startup.
• Carries forward the contribution from @overgoy in fix(core): survive a stale Windows log deleted mid-cleanup (#1211) #1215. Codex correctly identified that its regression test recursively called the patched Path.stat() on the supported Python 3.12 runtime.

What Changed

• Treat stale Windows log files that disappear during timestamp lookup as already pruned, allowing cleanup and logging setup to continue.
• Make the regression fixture keep file enumeration on the real filesystem, then trigger deletion specifically during the sort-key stat.
• Assert that the simulated race actually occurred so the test proves the production handler.

Implementation Details

• The first commit preserves @overgoy as author, retains the contributor DCO sign-off, and records original commit a00200e624162c62bfef6d00b44ba28d9030c7ad with cherry-pick -x.
• The production change from fix(core): survive a stale Windows log deleted mid-cleanup (#1211) #1215 remains unchanged. The second, separately signed maintainer commit only corrects and strengthens its regression test.
• This branch starts from current main, so it also includes changes landed after the contributor branch was created.

Testing

Automated

• uv run --python 3.12 pytest tests/utils/test_setup_logging.py::test_setup_logging_survives_a_stale_log_deleted_mid_cleanup -q before the maintainer fix: reproduced RecursionError.
• Same Python 3.12 targeted test after the fix: passed.
• uv run --python 3.12 pytest tests/utils/test_setup_logging.py -q: 10 passed.
• uv run pytest tests/utils/ -q: 166 passed.
• just fast-check: passed.

Manual

• No manual Windows run; the filesystem race is exercised deterministically at the failing boundary.

Risks / Follow-ups

• Scope is limited to stale per-process Windows log cleanup and its regression coverage.
• Supersedes fix(core): survive a stale Windows log deleted mid-cleanup (#1211) #1215. The contributor PR remains open until this replacement is reviewed and a closure decision is made.