Why: Keep the exact failed-sync receipt and the safe component reconciliation before retrying task synchronization.
Evidence: The Documents merge preserved both histories; materialization completed at Backend e6c3d0d87608f3053c89151e8d0cf3fa3f8788f1 and recursive check-worktree verify passed.
Impact: Task card only; no product change or stage-four acceptance claim.
Refs: stage 4 work-observation review; task-sync