rsync -a copies a read-only source dir (0555) as read-only, so the hourly
prune's rm -rf could not unlink inside it. From 2026-07-18 every pruned
snapshot was left as a 22-entry husk while the run still logged OK. The
1,740 husks on nh3-nas were removed (0 errors; 48 full snapshots kept).
The prune now runs chmod -R u+w before rm -rf, logs its error count and
the number of snapshots kept, and exits 3 on a failed prune (exit 1 on a
failed rsync) so the systemd unit shows failed instead of passing.
vh
de11e00dfb