Daemon-side library code: cleanup sweeper, nickname dedup saga, auto-room saga, and the on-disk event persister.
link() is called from the bin to ensure the inventory registrations
generated by #[myko_saga] / #[myko_command] survive dead-code
elimination. Message delivery itself is handled directly by the
marshal_entities::SendMessage and marshal_entities::BroadcastMessage
commands — there's no saga in the critical path for delivery.