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/api/v1/plugins.py

@@ -1232,14 +1232,20 @@ def _resolve_bridge_asset(name: str, instrument_type: str, path: Optional[str])
     base = os.path.basename((path or name).replace("\\", "/"))
     base_noext = os.path.splitext(base)[0].lower()
     # sf2/sf3/sfz: storage/soundfonts + system + user plugin_dirs
-    for base_dir in [UPLOAD_SF_DIR, SYSTEM_SF_DIR]:
+    sf_dirs = [UPLOAD_SF_DIR, SYSTEM_SF_DIR]
+    try:
+        from app.core.vst_engine import _load_user_plugin_dirs
+        sf_dirs += _load_user_plugin_dirs() or []
+    except Exception:
+        pass
+    for base_dir in dict.fromkeys(d for d in sf_dirs if d):
         if not os.path.isdir(base_dir):
             continue
-        for fname in os.listdir(base_dir):
-            cand = os.path.join(base_dir, fname)
-            if fname.lower().endswith((".sf2", ".sf3", ".sfz")) and \
-               (fname.lower() == base.lower() or os.path.splitext(fname)[0].lower() == base_noext):
-                return cand
+        for root, _, files in os.walk(base_dir):
+            for fname in files:
+                if fname.lower().endswith((".sf2", ".sf3", ".sfz")) and \
+                   (fname.lower() == base.lower() or os.path.splitext(fname)[0].lower() == base_noext):
+                    return os.path.join(root, fname)
     ext = (".vst3" if instrument_type.upper() == "VST3" else
            ".vst2" if instrument_type.upper() == "VST2" else
            ".sfz" if instrument_type.upper() == "SFZ" else None)
@@ -1249,8 +1255,12 @@ def _resolve_bridge_asset(name: str, instrument_type: str, path: Optional[str])
             dirs = _load_user_plugin_dirs() or []
         except Exception:
             dirs = []
-        if not dirs:
-            dirs = [settings.VST_DIR, settings.SOUNDFONT_DIR]
+        # Luon gop VST_DIR/SOUNDFONT_DIR: neu chi dung user plugin_dirs,
+        # VST trong C:/Program Files/Common Files/VST3 khong resolve
+        # duoc -> bridge load fail -> VSTi cam / khong mo GUI.
+        for d in (settings.VST_DIR, settings.SOUNDFONT_DIR):
+            if d and d not in dirs:
+                dirs.append(d)
         for base_dir in dirs:
             if not os.path.isdir(base_dir):
                 continue