- R1: when re-keying merges an intact body into a holder whose own body was
damaged, the rewritten holder leaves the damaged list, so the clear pass
no longer deletes it and unlinks the images just moved to it.
- R2: a losing duplicate apply removes a stage only when the store still
held it, never one another apply's job has taken.
- R3: a restore that times out waiting for requests keeps its review only
while it is unexpired and its slot is free; otherwise the stage goes and
the job says to try again.
- R4: a backup download cancelled while its snapshot is written removes
the snapshot once the worker finishes.