fix(audioout2): wire skipped-submit trace counter (#761)

src/SharpEmu.Libs/Audio/AudioOut2Exports.cs

@@ -921,6 +921,7 @@ public static class AudioOut2Exports
 
                 if (mixedPorts == 0)
                 {
+                    TraceSubmitSkipped(context, frames, "no-ports");
                     return false;
                 }
 
@@ -942,6 +943,7 @@ public static class AudioOut2Exports
                 var backend = ResolveContextBackend(context, out var backendName);
                 if (backend is null)
                 {
+                    TraceSubmitSkipped(context, frames, "no-backend");
                     return false;
                 }
 
@@ -1212,4 +1214,14 @@ public static class AudioOut2Exports
             Console.Error.WriteLine($"[LOADER][TRACE] audio_out2.{message}");
         }
     }
+
+    private static void TraceSubmitSkipped(ContextState context, int frames, string reason)
+    {
+        var n = Interlocked.Increment(ref _submitSkipTraceCount);
+        if (n <= 8 || n % 500 == 0)
+        {
+            TraceAudioOut2(
+                $"context-submit-skip#{n} handle=0x{context.Handle:X} frames={frames} reason={reason}");
+        }
+    }
 }