Implements the background loop (Go: monitorCluster) that reads RaftLogEntry
items from a channel and dispatches assignStream, removeStream, assignConsumer,
removeConsumer, and snapshot operations to JetStreamMetaGroup.
- Add five public mutation helpers to JetStreamMetaGroup (AddStreamAssignment,
RemoveStreamAssignment, AddConsumerAssignment, RemoveConsumerAssignment,
ReplaceAllAssignments) used by the monitor path
- JetStreamClusterMonitor: async loop over ChannelReader<RaftLogEntry>, JSON
dispatch, ILogger injection with NullLogger default, malformed entries logged
and skipped rather than aborting the loop
- WaitForProcessedAsync uses Monitor.PulseAll for race-free test synchronisation
with no Task.Delay — satisfies slopwatch SW003/SW004 rules
- 10 new targeted tests all pass; 1101 cluster regression tests unchanged
