PruneBlobs, CleanupLocalSnapshots, RemoveSnapshot, RemoveAllSnapshots
and snapshot purge wrote their status lines straight to stdout, so
`snapshot create --cron --prune` printed on every successful run and
--quiet did not silence `prune`, `snapshot purge`, `snapshot remove` or
`remote nuke`. Those lines now go through internal/ui, which drops them
under --cron and --quiet; warnings, errors and --json documents still
print.
The confirmation prompts still write straight to stdout, as the
`database delete` prompt does, together with what they ask to delete:
the snapshot list before the purge prompt, and the blob count and size
before the prune prompt. With --force those lines are status lines.
The two purge test fixtures gained the UI writer production always sets.
Model: opus-5-5
