V45: D17 seamless loop wrap + D18 stop solo note-off (Qin) + D18b/c guard + engine VST load fixes

- D17: wrap_info/wrap-skip, fx wrap xfade, playhead-derived scheduling
- D18: solo stop -> NOTE_OFF all sounding timeline pitches + CC123/CC120
- D18b: track audible gain guard, tracksRef fallback
- D18c: timelinePitchesRef per-track Set, kill at applyAllTrackMuteSolo
- bridge ring _MAX 16, index v=202608290928
- plugins.py/vst_engine.py/fx_realtime.py/JuceFxEngine.cpp: VSTi load + Qin fixes (uncommitted 12:18)

app/static/js/services/bridgeAudioNode.js

@@ -31,7 +31,7 @@
       console.warn('[BridgeAudioNode] AudioWorklet unavailable — ScriptProcessor fallback');
       return false;
     }
-    var url = '/static/js/services/bridgeAudioWorklet.js?v=202608272301';
+    var url = '/static/js/services/bridgeAudioWorklet.js?v=202608291200';
     _ctx.audioWorklet.addModule(url).then(function () {
       if (!_initialized) return; // disconnect() happened while loading
       if (_useWorklet) return;   // already set up (init retry)

app/static/js/services/bridgeAudioWorklet.js

@@ -1,6 +1,7 @@
 // app/static/js/services/bridgeAudioWorklet.js
 // VSTi crackle fix: audio sink chay tren audio thread (khong jank main thread).
-// - Ring block 256 mau, toi da 8 block (~42ms @48k) — hap thu jitter pump
+// - Ring block 256 mau, toi da 16 block (~85ms @48k) — hap thu jitter pump
+//   (option 2: 8->16 de dung tremolo crackle; backlog lon hon ~85ms)
 //   nhung gioi han backlog: 64 block (~371ms) tao tre ~0.3-0.4s khi play/
 //   keyboard preview (audio moi phai cho ring cu chay het).
 // - Underrun: fade ve 0 thay vi click (hard silence).
@@ -10,7 +11,7 @@ class BridgeAudioSinkProcessor extends AudioWorkletProcessor {
   constructor() {
     super();
     this._ring = [];
-    this._MAX = 8;
+    this._MAX = 16;
     this._gain = 1.0;
     this._lastOutL = 0.0;
     this._lastOutR = 0.0;