Fix Windows nanoserver NTFS permission issue and restore CI workflow

The test harness created C:\temp via the Docker tar API, which produces
SYSTEM-owned directories where ContainerUser only inherits
BUILTIN\Users:(RX) — insufficient for file deletion. Switch to
exec-based mkdir so ContainerUser gets FILE_DELETE_CHILD permission,
fixing remove and rename test failures on nanoserver.

Also suppress dead_code warning on condition_matches (reserved for
future tar-based search fallback) and restore the original CI workflow
that was replaced by the diagnostic workflow.

Author: chipsenkbeil