Replace pub/sub subscribe with XREADGROUP on bot game-start stream.
Remove dual-write from EventPublisher.publishGameStart.
Consumer group: bot-platform-consumer, XACK after forwarding.
Poll loop uses emitter identity to prevent thread leak on re-registration.
Group created with '$' offset — no historical replay on first connect.
Closes NCS-101
https://knockoutwhist.youtrack.cloud/issue/NCS-101
Reviewed-on: #63
Janis