V42+V42A: fix seam click khi loop master FX — worklet wrap crossfade (tail->head) + native WebAudio loop cho bypass (het click beat 0); dip bypass 5ms; PDC playhead freeze/snap

app/static/js/services/bridgeAudioWorklet.js

@@ -1,6 +1,8 @@
 // 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 64 block (~371ms @48k) — hap thu jitter pump.
+// - Ring block 256 mau, toi da 8 block (~42ms @48k) — hap thu jitter pump
+//   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).
 // - Resume sau silence: fade vao tu 0.
 // - Overrun: drop block cu nhat + crossfade 64 mau tai diem drop (het click).
@@ -8,7 +10,7 @@ class BridgeAudioSinkProcessor extends AudioWorkletProcessor {
   constructor() {
     super();
     this._ring = [];
-    this._MAX = 64;
+    this._MAX = 8;
     this._gain = 1.0;
     this._lastOutL = 0.0;
     this._lastOutR = 0.0;