fix: GUI VST native window qua bridge + audio path bridge (SF2 preview/play câm)

- open_vst_gui: bo WebviewWindowBuilder/thread, chi push_control type=4 (hwnd=0 -> bridge tao window)
- main.cpp: create_native_vst_window (class SonicForge_Native_VST3_Class, 800x600, khong TOPMOST),
  tao trong ChannelWorker job, map guiWindows, capture arg2 by value (fix dangling)
- app.jsx: guard isBridgeActive() 8 cho -> bridge active thi moi note di router -> pushEvent -> bridge
  (truoc day SF2 cam vi HAS_PYFLUIDSYNTH=FALSE -> /soundfont-render 501; VST3 path cu dung nativeSf/Carla)
- E2E: SF2 NOTE_ON qua dispatchMidiEvent -> SHM peak 0.029745; Nexus GUI native hwnd OK (license/preset)
- docs: TASKS.md + TEST_NOTES.md ghi batch fix + ket qua; gitignore vendor/junk

app/static/js/services/nativeBridgeService.js

@@ -20,6 +20,30 @@
       if (this._statusCb) this._statusCb({ connected: !!connected });
     },
 
+    /** Fix C: re-establish bridge routing once audio frames arrive again
+     *  after bridge-down. Same wiring as the bootstrap block in app.jsx
+     *  (getAudioContext -> BridgeAudioNode.init -> AudioRoutingEngine.connect). */
+    _reconnectInFlight: false,
+    _reconnectIfNeeded: function () {
+      if (this._reconnectInFlight) return;
+      this._reconnectInFlight = true;
+      var self = this;
+      var finish = function () { self._reconnectInFlight = false; };
+      try {
+        var ctx = (typeof getAudioContext === 'function') ? getAudioContext() : (window.__sharedAudioCtx || null);
+        if (ctx && window.BridgeAudioNode && window.AudioRoutingEngine) {
+          window.BridgeAudioNode.init(ctx);
+          window.AudioRoutingEngine.connect(window.BridgeAudioNode, null, null);
+        }
+        if (window.SonicMidiRouter) window.SonicMidiRouter.setBridgeConnected(true);
+        this._notifyStatus(true);
+        console.warn('[BridgeService] bridge recovered — routing re-established.');
+      } catch (e) {
+        console.warn('[BridgeService] reconnect failed:', e);
+      }
+      finish();
+    },
+
     _init: function () {
       if (!this._tauri()) {
         // Dev mode (Linux / plain browser): no Tauri -> log-only, app uses SonicSF.
@@ -29,6 +53,9 @@
       var self = this;
       try {
         window.__TAURI__.event.listen('bridge-audio', function (e) {
+          // Bridge recovered after bridge-down (or never bootstrapped):
+          // audio frames flow again -> re-establish routing (Fix C).
+          if (!self.isBridgeConnected) self._reconnectIfNeeded();
           if (self._audioCb) self._audioCb(e.payload.l, e.payload.r);
         });
         window.__TAURI__.event.listen('bridge-down', function () {