fix(v9): 5 bugs — GUI deferred until VST loaded (no white window), fixed retry 8x500ms, VST3 folder resolve for auto-load, sustain-CC64 dropped after STOP, taskkill process tree on exit, Synth+GUI same row in TCP

app/api/v1/plugins.py

@@ -1269,6 +1269,16 @@ def _resolve_bridge_asset(name: str, instrument_type: str, path: Optional[str])
                     if fn.lower().endswith(ext) and \
                        (fn.lower() == base.lower() or os.path.splitext(fn)[0].lower() == base_noext):
                         return os.path.join(root, fn)
+            # V9 bug 8: Windows VST3 = FOLDER "X.vst3" (chua X.vst3.dll) —
+            # khong la file nen file-walk tren khong thay -> resolve null ->
+            # bridge load fail -> VSTi khong auto-load khi mo project. Scan
+            # sub-folder trung ten: "x.vst3" == base.lower() hoac "x" ==
+            # base_noext.
+            for sub in os.listdir(root):
+                sp = os.path.join(root, sub)
+                if os.path.isdir(sp) and sub.lower().endswith(ext) and \
+                   (sub.lower() == base.lower() or os.path.splitext(sub)[0].lower() == base_noext):
+                    return sp
     return None
 
 @router.post("/bridge/load")