[idd] audio: add mediated broker control endpoint

Expose a private, versioned control device that lets the IDD discover
and claim the active audio adapter without using the public PortCls
endpoints.

Restrict access to SYSTEM and UMDF hosts, track adapter and binding
generations, and keep broker failure optional. Reserve data-plane
capabilities without advertising them until PCM queues are available.

idd/LGAudio/Adapter.cpp

@@ -19,6 +19,7 @@
  */
 
 #include "Adapter.h"
+#include "BrokerDevice.h"
 #include "Formats.h"
 #include "MiniportTopology.h"
 #include "MiniportWaveRT.h"
@@ -237,6 +238,17 @@ NTSTATUS StartAudioDevice(
     status = PcRegisterPhysicalConnection(deviceObject, topologyCapture,
       kCaptureTopologyBridgePin, waveCapture, kCaptureWaveBridgePin);
 
+  if (NT_SUCCESS(status))
+  {
+    const NTSTATUS brokerStatus =
+      BrokerDeviceAttachAdapter(deviceObject, adapter);
+    if (!NT_SUCCESS(brokerStatus))
+    {
+      LGAUDIO_TRACE_ERROR("broker adapter unavailable: 0x%08X",
+        brokerStatus);
+    }
+  }
+
   SafeRelease(waveCapture);
   SafeRelease(topologyCapture);
   SafeRelease(waveRender);