feat(host-agent): include mcp_busy_device_ids in heartbeat payload

apps/device-host-agent/host_agent/heartbeat.py

@@ -14,6 +14,8 @@ from host_agent.status import AgentStatusTracker
 if TYPE_CHECKING:
     from collections.abc import Awaitable, Callable
 
+    from host_agent.mcp_lock import McpBusyTracker
+
 
 def build_device_snapshot(manager: DeviceManager) -> list[DeviceSnapshotModel]:
     return [
@@ -40,6 +42,7 @@ class HeartbeatSynchronizer:
         on_sync: Callable[[int], None] | None = None,
         policy_cache: HostPolicyCacheStore | None = None,
         on_policy_sync: Callable[[int], None] | None = None,
+        mcp_busy_tracker: McpBusyTracker | None = None,
     ) -> None:
         self.manager = manager
         self.client = client
@@ -50,6 +53,7 @@ class HeartbeatSynchronizer:
         self.on_sync = on_sync
         self.policy_cache = policy_cache
         self.on_policy_sync = on_policy_sync
+        self.mcp_busy_tracker = mcp_busy_tracker
         self.policy = policy_cache.load() if policy_cache is not None else None
         self.policy_revision = self.policy.revision if self.policy is not None else 0
         if self.status_tracker is not None:
@@ -57,10 +61,16 @@ class HeartbeatSynchronizer:
 
     async def sync_once(self) -> HeartbeatResponse:
         snapshot = build_device_snapshot(self.manager)
+        mcp_busy_ids = (
+            self.mcp_busy_tracker.busy_device_ids()
+            if self.mcp_busy_tracker is not None
+            else []
+        )
         response = await self.client.heartbeat(
             snapshot,
             address=self.address,
             policy_revision=self.policy_revision,
+            mcp_busy_device_ids=mcp_busy_ids,
         )
         self.policy_revision = response.policy_revision
         if response.policy is not None: