Add VST2 hosting to native bridge; fix CC7 data2 routing verified via SHM test

VST2 (Steinberg 2.4 ABI) host via Vst2Instrument: aeffect.h, dispatcher,
process events/replacing, kEffectStartProcess, headless GUI skip.
- create_instrument returns Vst2Instrument for InstrumentType::VST2
- 64B-aligned scratch buffers for SIMD plugins; SEH crash capture module+stack
- plugins.py: VST2 resolves .dll/.so; vst_engine.py reports VST2 type
- app.jsx: derive instrumentType from scan (VST3 vs VST2), not hardcoded
- Install exes refreshed from Release build

SF2 FluidSynth audio verified end-to-end through SHM ring (energy 1.33):
silence was a test-harness bug (CC7 value written to velocity field, bridge
reads data2) — app sends data2 correctly. All temporary diagnostics removed.

native_bridge/src/main.cpp

@@ -793,6 +793,16 @@ int main(int argc, char* argv[]) {
             g_pendingGui[guiCh] = { (void*)arg1, pluginId };
             return;
         }
+        // VST2 headless (no editor) hoac instrument load fail -> khong tao
+        // window, khong reuse window cua channel khac (window trong voi title
+        // sai plugin). Frontend hien "VST2 headless - no GUI" thay vi window.
+        if (instruments.withInstrument(guiCh, [](INativeInstrument* i0) {
+                return !i0 || !i0->canOpenGUI();
+            })) {
+            std::cerr << "[NativeBridge] GUI skip ch=" << guiCh
+                      << " plugin=" << pluginId << " (headless - no editor)" << std::endl;
+            return;
+        }
         // Dedupe OPEN_GUI spam (frontend openVstGuiRetry): view dang
         // attached -> GUI da mo, khong post attach job lan nua. Re-attach
         // tren view dang attached lam plugin loi (Nexus createView null).