[host] measure ready time at framebuffer publication

Exclude command queue reset and cleanup from the ready stage, and keep
the wall-clock residual only as the legacy timing fallback.

client/src/main.h

@@ -154,6 +154,7 @@ struct AppState
   atomic_uint_least64_t producerCaptureTime;
   atomic_uint_least64_t producerPostProcessTime;
   atomic_uint_least64_t producerCopyTime;
+  atomic_uint_least64_t producerReadyTime;
   atomic_uint_least64_t clientImportTime;
   atomic_uint_least64_t renderCount, frameCount;
   _Atomic(float)        fps, ups;