7116988d03
C7: JetStreamApiRouter now checks leadership before mutating operations. Non-leader nodes return error code 10003 with a leader_hint field. JetStreamMetaGroup gains IsLeader() and Leader for cluster-aware routing. C8: StreamApiHandlers.HandlePurge accepts PurgeRequest options (filter, seq, keep). StreamManager.PurgeEx implements subject-filtered purge, sequence-based purge, keep-last-N, and filter+keep combinations.