[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/overlays.h

@@ -50,6 +50,7 @@ typedef struct OverlayFrameTiming
   float    capture;
   float    postProcess;
   float    copy;
+  float    ready;
   float    import;
   float    render;
 }