fix(bridge): load dung VSTi theo track (V9) - bo early-return mui theo flag, load qua Tauri invoke khi co path, guard path sai (WaveObserver vs Nexus), chi mo GUI khi load OK; sync 6 ban JS + index.html ?v; kem cac fix bridge truoc (bugs 1-4, GUI restore)

native_bridge/include/NativeInstrumentEngine.h

@@ -156,17 +156,22 @@ public:
 
 private:
     static std::unique_ptr<INativeInstrument> create_instrument(InstrumentType type);
+    // Probe-render 3 notes sau khi load, do peak, tinh makeup de note don ra
+    // ~ -6 dBFS (0.5) - can bang am luong moi engine (VST2/VST3/SF2/SFZ).
+    static float calibrate(INativeInstrument* inst, double sampleRate, uint32_t blockSize);
 
     mutable std::mutex mu_;
     std::map<uint32_t, std::unique_ptr<INativeInstrument>> channels_;
     std::map<uint32_t, std::string> paths_;  // last assigned path per channel
     std::map<uint32_t, InstrumentType> types_;  // last assigned type per channel (G2.1)
+    std::map<uint32_t, float> makeup_;  // calibrated per-channel output gain (renderAll ap dung)
     // Per-instrument scratch so engines that overwrite (not mix) stay additive.
     std::vector<float> scratchL_, scratchR_;
     // Channel-level reload flag (see isReloading) — indexed by MIDI channel.
     bool reloadingCh_[16] = {};
     // G3.3: channel muted after a plugin fault inside processAudioBlock.
     bool crashedCh_[16] = {};
+    float limiterGain_ = 1.0f;  // smoothed mix limiter state (renderAll)
     // True when the channel's plugin DLL has an attached editor (or its reload
     // is in progress): real-time code drops MIDI and skips rendering. Lowercased
     // compare inside -- Windows plugin paths are case-insensitive.