controller: UI-toggle audio output + astreamselect decouple (Phase 7 Вариант 2)

Web UI checkbox в Audio source карточке: «вывод аудио в стрим». Off →
TV получает silence + downstream audio chain isolated от live-audio RTSP
(нестабильный sidecar поток больше не блокирует video pipeline).

Изменения:
  state.InstanceState: + audio_output_enabled (default True)
  config.InstanceCfg:
    + audio_output_volume_target (default volume@output_audio)
    + audio_input_select_target (default astreamselect@audio_input)
  dispatch.set_audio_output_enabled(enabled):
    enabled=False → astreamselect map=1 (anullsrc) + volume=0
    enabled=True  → astreamselect map=0 (live-audio) + volume=1
    Двойная команда: select decouples upstream, volume гарантирует тишину
    на случай если в anullsrc что-то не так.
  http_api: + GET /audio-output/{instance}, POST /audio-output/{instance}
  static/index.html: + checkbox в Audio source header + loadAudioOut/toggleAudioOut

ZMQ smoke test OK. HTTP roundtrip OK.

Сопутствующий pipeline change: docker-compose.phase7.yml — amix заменён
на astreamselect@audio_input (см. localhost-infra commit).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

controller/cuda_grid_controller/dispatch.py

@@ -218,6 +218,39 @@ class CommandDispatcher:
         использует cell 0 как main slot. Семантика идентична: cell_map 0 = cam_index."""
         await self.set_main_cam(instance, cam_index)
 
+    async def set_audio_output_enabled(self, instance: str, enabled: bool) -> bool:
+        """Phase 7 Вариант 2: mute = astreamselect map=1 (anullsrc) + volume=0.
+        unmute = astreamselect map=0 (live-audio) + volume=1. astreamselect
+        decouples downstream от jittery live-audio RTSP — при mute frames
+        идут только через anullsrc chain, video не зависит от audio sidecar."""
+        inst = self._find_instance(instance)
+        if inst is None:
+            return False
+        client = self._client(inst)
+        input_map = "0" if enabled else "1"
+        volume = "1.0" if enabled else "0.0"
+        try:
+            reply1 = await client.send_command(
+                inst.audio_input_select_target, "map", input_map
+            )
+            reply2 = await client.send_command(
+                inst.audio_output_volume_target, "volume", volume
+            )
+            log.info("dispatch.audio_output_set",
+                     instance=instance, enabled=enabled,
+                     input_map=input_map, volume=volume,
+                     select_reply=reply1, volume_reply=reply2)
+        except (TimeoutError, Exception) as e:
+            log.warning("dispatch.audio_output_fail",
+                        instance=instance, error=str(e))
+            return False
+        await self.state.set_audio_output_enabled(instance, enabled)
+        if self.on_state_change:
+            await self.on_state_change(instance, "audio_output", "on" if enabled else "off")
+        if self.on_event:
+            await self.on_event(instance, "audio_output_changed", {"enabled": enabled})
+        return True
+
     async def _reload_icon(self, instance: str, icon_name: str) -> None:
         """Invalidate cached icon atlas во всех cuda_grid instances — каждый
         имеет свой кеш."""