V45.2 fix Qin silence (20s audio-thread stall) + SF loop downbeat delay

- SandboxVst2Host::loadSerializedState: queuePreset non-blocking (byte-identical
  echo never matched -> waitApply always burned 20s TIMEOUT on the audio thread;
  VST2 restore runs via runOnMain so every startup silenced ALL audio ~20s = Qin
  'failed that su'). Bridge now holds reloading + defers saveStateJob until the
  child republishes a different chunk (clobber protection, no audio block).
- sf-fx-realtime clear_queue('loop'): truncate old tail to KEEP=4 blocks
  (~21ms) instead of keeping FILL 24 (~128ms) -> wrap downbeat no longer ~110ms
  late; skipFade crossfade masks the truncation jump, seam crossfade recount.
- bump ?v= 202608291721 (app.jsx x2, index.html x2); deploy 3 _internal + dist.

app/static/js/app.jsx

@@ -1907,7 +1907,7 @@ async function fxRtStart() {
   fxRt.sessionId = st.session_id;
   fxRtGuiPushShm();
   try {
-    await ctx.audioWorklet.addModule(`${API_BASE_URL}/static/js/sf-fx-realtime.js?v=202608272300`);
+    await ctx.audioWorklet.addModule(`${API_BASE_URL}/static/js/sf-fx-realtime.js?v=202608291721`);
     if (token !== fxRt.startToken) { fxRt.starting = false; return; }
     fxRt.node = new AudioWorkletNode(ctx, 'sf-fx-realtime', { numberOfInputs: 1, numberOfOutputs: 1, outputChannelCount: [2] });
     const u = new URL(API_BASE_URL);
@@ -24820,7 +24820,7 @@ const App = () => {
     fxRtTracks[key] = entry;
     fxRtGuiPushShm();
     try {
-      await ctx.audioWorklet.addModule(`${API_BASE_URL}/static/js/sf-fx-realtime.js?v=202608272300`);
+      await ctx.audioWorklet.addModule(`${API_BASE_URL}/static/js/sf-fx-realtime.js?v=202608291721`);
       const node = new AudioWorkletNode(ctx, 'sf-fx-realtime', { numberOfInputs: 1, numberOfOutputs: 1, outputChannelCount: [2] });
       entry.node = node;
       const u = new URL(API_BASE_URL);