05565ee8a2
The helper keys its sandbox on std::process::id() under env::temp_dir(), so the pre-create wipe never matches a prior run's path: one directory strands per test-binary invocation on the 16 GiB tmpfs (>50k dirs by 2026-07-13). The test pins the property at one representative site: the returned path embeds no PID and lives off env::temp_dir(). refs #258