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fleetd#341: per-name guard so a later spawns different unprotected credential name still warns
fleetd #339: guard backend error sink
#338: cancel timed-out queued deliveries
fleetd#333: fleet.leaders is split, and split membership now proves reporting exists
fleetd#329: fix silent async-ticket bugs in MessageService (F1/F2/F3)
fleetd#330: split reload class for health/coordinator + top-level coverage
fleetd#326: classify primary and configReload as deferred top-level keys