#4397 On Windows, removeStaleOutputSummaries warns when two clears race, failing output_summary_index_test intermittently

src/infrastructure/persistence/output_summary_index_test.ts:721 (removeStaleOutputSummaries: clears racing each other warn of nothing, and leave no shard) fails intermittently on Windows: 12 of the 29 Windows Compatibility runs since 2026-10-31 00:15Z, most recently https://github.com/swamp-club/swamp/actions/runs/41864132261 on dd6591148.

The test expects no warnings, but gets:

"Clearing the output summaries of C:\Users\[REDACTED]\AppData\Local\Temp\swamp-test-… failed. Reads still check each row against its record, but the rows stay on disk. Delete C:\Users\[REDACTED]\AppData\…"

When two clears race, one fails a delete or rename that the other holds open or has already moved. On Windows that probably raises os error 32 or 5 (PermissionDenied), where POSIX raises NotFound or succeeds. The clear treats that error as a real failure and warns. The test was added with the summary index in 24be9a5b9 (swamp-club#4145). The intermittent failure suggests a real race on Windows, not a deterministic path mismatch.