gza-system-triage

Turn the recurring watch stuck-task pile into (1) a diagnosis of why each class is stuck, (2) the existing stuck rows actually cleared now, and (3) systemic prevention so it does not recur. Snapshots watch/incomplete/queue, buckets stuck tasks by failure class, dedups against already-tracked system work, unsticks each row by its clearing action (drop moot/dead/stale, spawn follow-up, hand review-loop rows to /gza-task-fix), then ranks and files system-tagged prevention fixes by blast radius (cascade-preventer first). Never merges, retries, resumes, deletes branches, or edits code.