Drain it, stop it, and put it back verifiedWritten by the Hub

A MailerQ node has no spool: its work lives in the broker and in memory. Stopping the service with messages in memory loses the memory half — those messages return to the queue only if they were not acknowledged, and the ones being sent are in an uncertain state. So the sequence matters. Stop the inflow, let the in-memory set drain, and use a pause rather than a signal for whatever is left. The pause is reversible and visible; a stopped service is neither. The detail that catches people: the queue a node reads is rabbitmq-queue if set, otherwise rabbitmq-outbox, and the delay ladder inherits that name. On a node that was renamed, the queue called outbox may be nobody's.