feat: coordinate authoritative playback and audio routing

config.yaml

@@ -8,6 +8,8 @@ mqtt:
   reconnect_min_seconds: 1
   reconnect_max_seconds: 30
   command_queue_size: 512
+  # QoS 1 is accepted only after the broker PUBACKs within this bound.
+  publish_ack_timeout_seconds: 2
 
 topics:
   player_command: youtube/player/cmd
@@ -19,8 +21,9 @@ topics:
   playback_base: youtube/media/playback
   router_mode_set: audio/player/mode/set
   router_mode_state: audio/player/mode/state
-  # Optional additive result topic. Existing consumers do not depend on it.
-  controller_result: null
+  # Optional additive result/warning topic. Set null to disable it.
+  # Existing consumers never depend on this topic.
+  controller_result: youtube/controller/v2/events
 
 storage:
   media_base: /mnt/Media/YTPlayer