Fix AI proxy origin in Tauri, SF2 program_select, VSTi GUI reopen + sample rate bridge

- aiGateway.js: use window.API_BASE_URL (engine port) instead of window.location.origin (tauri://localhost asset protocol returned index.html -> JSON parse error); check content-type before parsing response
- NativeInstrumentEngine.cpp: fluid_synth_program_select for SF2 instrument + program change
- Vst3Instrument.cpp: activate all audio/event buses, channel=0 forced, GUI resize/reopen, kEvent using fix
- main.cpp: VST GUI reopen via WM_DESTROY, OleInitialize, steady_clock loop
- lib.rs: BridgeSampleRate state, restart_bridge_with_sample_rate command, borrow fix
- app.jsx/nativeBridgeService.js: isMidiTrack widening, bridge masterbus connect, held MIDI notes, sample-rate restart, openNativeGUI channel

native_bridge/src/main.cpp

@@ -14,9 +14,9 @@
 #include <unistd.h>
 #include <cstdlib>
 #include <thread>
-#include <chrono>
 #endif
 
+#include <chrono>
 #include <algorithm>
 #include <condition_variable>
 #include <cstring>
@@ -48,6 +48,19 @@ static void sleep_ms(uint32_t ms) {
 #endif
 }
 
+#ifdef _WIN32
+static LRESULT CALLBACK VstWindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) {
+    if (uMsg == WM_DESTROY) {
+        void* ptr = (void*)GetWindowLongPtrA(hwnd, GWLP_USERDATA);
+        if (ptr) {
+            INativeInstrument* inst = static_cast<INativeInstrument*>(ptr);
+            inst->closeGUI();
+        }
+    }
+    return DefWindowProcA(hwnd, uMsg, wParam, lParam);
+}
+#endif
+
 // B9: native Win32 window for the VST editor (replaces the WebView2 surface —
 // the HTML window was drawn ON TOP of the plugin GUI). MUST be created on the
 // ChannelWorker thread so the worker's idle message pump services its messages.
@@ -57,7 +70,7 @@ static void* create_native_vst_window(const char* title) {
     static bool registered = false;
     if (!registered) {
         WNDCLASSA wc = {};
-        wc.lpfnWndProc = DefWindowProcA;
+        wc.lpfnWndProc = VstWindowProc;
         wc.hInstance = GetModuleHandleA(nullptr);
         wc.lpszClassName = kWndClass;
         RegisterClassA(&wc);
@@ -86,7 +99,7 @@ public:
     ChannelWorker() {
         th_ = std::thread([this] {
 #ifdef _WIN32
-            CoInitializeEx(nullptr, COINIT_APARTMENTTHREADED);
+            OleInitialize(nullptr);
 #endif
             std::unique_lock<std::mutex> lk(mu_);
             for (;;) {
@@ -112,7 +125,7 @@ public:
                 lk.lock();
             }
 #ifdef _WIN32
-            CoUninitialize();
+            OleUninitialize();
 #endif
         });
     }
@@ -229,6 +242,10 @@ int main(int argc, char* argv[]) {
         instruments.renderAll(shmIPC->masterLeft + from, shmIPC->masterRight + from, to - from);
     };
 
+    double blockDurationMs = (double)block / sampleRate * 1000.0;
+    auto startTime = std::chrono::steady_clock::now();
+    uint64_t blockCount = 0;
+
     // 2. REAL-TIME AUDIO PROCESSING ENGINE LOOP
     while (true) {
 #ifdef _WIN32
@@ -289,8 +306,6 @@ int main(int argc, char* argv[]) {
                     playheadSamples = c.arg1;
                 }
             } else if (c.type == 4) { // OPEN_GUI (A7): arg1 = parent HWND (0 → bridge tự tạo native window), arg2 = plugin id
-                // ponytail: per-plugin channel mapping chua co — gan GUI cho
-                // instrument dau tien duoc load (smoke test = 1 instrument).
                 // Chay tren CUNG ChannelWorker da load instrument: thread rieng
                 // cho openGUI lai tao COM apartment moi, con plugin thi song o
                 // apartment cu da chet (load thread exit) -> Nexus attached()
@@ -299,16 +314,14 @@ int main(int argc, char* argv[]) {
                 // 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 (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);
+                uint32_t guiCh = c.channel;
+                if (guiCh >= 16) guiCh = 0;
+                for (int tries = 0; tries < 200 && !instruments.get(guiCh); ++tries) {
+                    sleep_ms(50);
                 }
-                if (guiCh == 16) {
+                if (!instruments.get(guiCh)) {
                     std::cerr << "[NativeBridge] GUI attach FAILED hwnd=" << c.arg1
-                              << " plugin=" << c.arg2 << " (no instrument loaded)" << std::endl;
+                              << " plugin=" << c.arg2 << " ch=" << guiCh << " (no instrument loaded)" << std::endl;
                 } else {
                     if (!workers[guiCh]) workers[guiCh] = std::make_unique<ChannelWorker>();
                     workers[guiCh]->post([&instruments, &guiWindows, guiCh, arg1 = c.arg1, arg2 = std::string(c.arg2)]() {
@@ -317,14 +330,27 @@ int main(int argc, char* argv[]) {
                         void* hwnd = (void*)(uintptr_t)arg1;
 #ifdef _WIN32
                         if (arg1 == 0) {
-                            // B9: bridge tự tạo native window — editor VST3 đính
-                            // vào đây; message pump bởi ChannelWorker idle loop.
-                            hwnd = create_native_vst_window(arg2.c_str());
-                            if (!hwnd) {
-                                std::cerr << "[NativeBridge] GUI create window FAILED plugin=" << arg2 << std::endl;
-                                return;
+                            HWND existingHwnd = nullptr;
+                            auto it = guiWindows.find(guiCh);
+                            if (it != guiWindows.end()) {
+                                existingHwnd = (HWND)it->second;
+                            }
+                            if (existingHwnd && IsWindow(existingHwnd)) {
+                                hwnd = existingHwnd;
+                                SetWindowTextA((HWND)hwnd, arg2.c_str());
+                                ShowWindow((HWND)hwnd, SW_SHOW);
+                                SetForegroundWindow((HWND)hwnd);
+                            } else {
+                                hwnd = create_native_vst_window(arg2.c_str());
+                                if (!hwnd) {
+                                    std::cerr << "[NativeBridge] GUI create window FAILED plugin=" << arg2 << std::endl;
+                                    return;
+                                }
+                                guiWindows[guiCh] = hwnd; // keep window alive
+                                if (auto* inst = instruments.get(guiCh)) {
+                                    SetWindowLongPtrA((HWND)hwnd, GWLP_USERDATA, (LONG_PTR)inst);
+                                }
                             }
-                            guiWindows[guiCh] = hwnd; // keep window alive
                         }
 #else
                         (void)guiWindows;
@@ -376,8 +402,19 @@ int main(int argc, char* argv[]) {
             break;
         }
 
-        // E. Sleep briefly for the next frame tick (block@44100 ≈ 5.8ms)
-        sleep_ms(1);
+        // E. Synchronize with real-time audio playback
+        blockCount++;
+        auto targetTime = startTime + std::chrono::microseconds(static_cast<int64_t>(blockCount * blockDurationMs * 1000.0));
+        auto now = std::chrono::steady_clock::now();
+        if (now < targetTime) {
+            auto diff = std::chrono::duration_cast<std::chrono::microseconds>(targetTime - now).count();
+            if (diff > 1000) {
+                sleep_ms(diff / 1000);
+            }
+            while (std::chrono::steady_clock::now() < targetTime) {
+                std::this_thread::yield();
+            }
+        }
     }
 
 #ifdef _WIN32