Local run showed TestLifecycleNoncurrentVersionExpiration failing
with a bare 404 on HEAD(latest), not enough to tell whether v2 was
deleted, the bare-key pointer was removed, or a delete marker was
synthesized. Strengthen the test to:
- HEAD by versionId=v2 first, so we pin "v2 file still on disk"
separately from "the latest pointer resolves to v2"
- on HEAD(latest) failure, log ListObjectVersions output (versions +
markers, with IsLatest) so the next failure shows which side the
bug is on rather than just NotFound