fix: SF2 sound (audio sink FIFO underrun) + VST3 native GUI open + GUI load race

- bridgeAudioNode: ScriptProcessor 4096 drained only 1 of 16 blocks -> ~94% silence; now drains all queued blocks per callback, RING_DEPTH 8->24
- app.jsx: openNativeGUI had NO caller; wire after VST3 loadInstrument OK in track Synth dropdown + Plugin Manager Load Bridge
- main.cpp: OPEN_GUI polls up to 10s for LOAD completion (worker thread) before attach - fixes race 'no instrument loaded'
- index.html: bump bridgeAudioNode/app.precompiled cache versions

native_bridge/src/main.cpp

@@ -295,9 +295,16 @@ int main(int argc, char* argv[]) {
                 // cho openGUI lai tao COM apartment moi, con plugin thi song o
                 // apartment cu da chet (load thread exit) -> Nexus attached()
                 // hang (gui_probe: bridge_like treo, same_thread OK).
+                // LOAD va OPEN_GUI duoc drain trong cung vong lap: LOAD post job
+                // len worker (async, VST3 init co the mat giay) truoc khi type=4
+                // duoc xu ly — khong doi, instruments.get() con rong -> "no
+                // instrument loaded". Poll toi da 10s cho LOAD hoan tat.
                 uint32_t guiCh = 16;
-                for (uint32_t ch = 0; ch < 16; ++ch) {
-                    if (instruments.get(ch)) { guiCh = ch; break; }
+                for (int tries = 0; tries < 200 && guiCh == 16; ++tries) {
+                    for (uint32_t ch = 0; ch < 16; ++ch) {
+                        if (instruments.get(ch)) { guiCh = ch; break; }
+                    }
+                    if (guiCh == 16) sleep_ms(50);
                 }
                 if (guiCh == 16) {
                     std::cerr << "[NativeBridge] GUI attach FAILED hwnd=" << c.arg1