Add the CB-586 retention rule to GitWorktrees and drive it from the reaper:
a snapshot is deleted only when its tree content is already reachable from
main AND the ref is older than 24h. Reachability keeps the last copy of a
worker's work; the age floor stops a fresh snapshot being swept while a
lead is still looking at it. Every deletion logs the ref name and commit
sha so it is recoverable from the reflog. The /members response gains a
wipRefs{count,costBytes} census the operator can read without shelling
into the repo.
Dai Ha
0efe1567c0