Quiesce loop resumes (StartStack + clear marker) at the snapshotted phase
instead of done -> downtime whole-backup -> until-snapshot, no consistency loss.
Keeps polling to done/failed (no overlapping backup; post-snapshot failure
observed). Stop-mode fallback to done + crash-safety preserved.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
