6531ec1984
After the fleet splits into one Akka mesh per application Cluster, a ClusterClientReceptionist serves only its own mesh — so the single fleet-wide client's SendToAll reached only the mesh whose receptionist answered, leaving every other cluster silently on its old configuration. Central now holds one ClusterClient per ClusterId and fans SendToAll across all of them. LoadContactsFromDb selects ClusterId and groups the receptionist contacts per cluster (keeping the per-row TryParse guard and the enabled/non-maintenance filter); ContactsLoaded carries ContactsByCluster; HandleContactsLoaded diffs per cluster (rebuild changed, stop+drop vanished, warn-don't-create on empty); RebuildClient builds a per-cluster client under a clusterId-derived actor name. IMeshClusterClientFactory.Create gained a clusterId parameter so the per-cluster clients get distinct, diagnosable names. ApplyAck handling and the DPS branch are unchanged; the deploy path stays payload-free. Tests: focused unit coverage of the grouping + fan-out (one-client-per-cluster, fan-out SendToAll to every cluster client) via the recording factory double, plus the real two-mesh boundary test extended to central + two separate site meshes proving one dispatch reaches both and a client scoped to one cluster never crosses into another. Red-before-green verified: crippling the fan-out to a single client fails the reaches-both-meshes assertion. Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW