Unmount, and optionally delete, EC volume shards from the shell, so broken
or over-replicated shards can be handled without stopping volume servers and
deleting files by hand.
Default action is unmount; --delete also removes the shard files. Targets
resolve against the live topology, with shardId:host:port to disambiguate
co-located or over-replicated shards. Dry-run by default; pass --apply.