fix(fx-rt): het crackle master FX - limiter attack smooth + crossfade khi bat/tat chain

- NativeInstrumentEngine: kAttack 0.9->0.1 (het zipper khi sum nhieu track)
- app.jsx: crossfade masterFxDryGain/masterFxGain thay hard-rewire graph luc
  activation/deactivation master chain FX; worklet bao 'started' -> ramp dung
  luc; PDC tre sau khi dry silent (tranh gap 80ms)
- sf-fx-realtime.js: fade-in 512 mau luc FILL xong / resume sau underrun
- index.html + addModule: cache-buster v=202608241200
- rebuild app.precompiled.js, copy bundle vao dist/ + src-tauri/resources/
- keo dai fix cac round truoc: FILL 16, FXRT_BURST_MS, REBUFFER, pacing,
  VST GUI click/focus, solo crackle
- them harness + plans/patch scripts

native_bridge/src/RenderFxJob.cpp

@@ -1639,6 +1639,7 @@ static void fxGuiFeedLoop(Vst3Fx* fx, HWND hwnd, std::shared_ptr<FxGuiShmCtl> ct
     FxRealtimeIPC* ipc = nullptr;
     std::string curName;
     uint64_t lastWrite = 0;  // feeder-local: newest inWrite already peeked
+    auto nextTick = std::chrono::steady_clock::now();
     while (IsWindow(hwnd)) {
         std::string name;
         {
@@ -1665,7 +1666,16 @@ static void fxGuiFeedLoop(Vst3Fx* fx, HWND hwnd, std::shared_ptr<FxGuiShmCtl> ct
                 lastWrite = ipc->h.inWrite;
             }
         }
-        Sleep(2);
+        // Pace the feeder to realtime (one FXRT_BLOCK per its audio duration,
+        // 44.1k fallback) instead of Sleep(2) busy-spin (~3x realtime CPU).
+        // Less CPU in the GUI process = less contention with the pump thread,
+        // which was stalling /input (dead clicks) and /preset (crackle reloads).
+        const uint32_t sr = (ipc && ipc->h.sampleRate > 0) ? ipc->h.sampleRate : 44100u;
+        nextTick += std::chrono::microseconds(1000000ULL * FXRT_BLOCK / sr);
+        const auto now = std::chrono::steady_clock::now();
+        if (now > nextTick + std::chrono::milliseconds(50))
+            nextTick = now;  // fell behind (plugin hiccup): resync, don't burst
+        std::this_thread::sleep_until(nextTick);
     }
     if (v) fxGuiCloseShm(v);
 }
@@ -1690,7 +1700,7 @@ static void fxGuiStartFeederThread(Vst3Fx* fx, HWND hwnd) {
 
 // --- split setup for server mode (startup speed) -----------------------------
 // 1. Parse job { path, name } — fast. Returns 0 ok, 1 job/argument error.
-static int fxGuiParseJob(const std::string& jobPath, std::string& path, std::string& name, std::string& shm) {
+static int fxGuiParseJob(const std::string& jobPath, std::string& path, std::string& name, std::string& shm, std::string& presetB64) {
     std::ifstream jf(jobPath, std::ios::binary);
     if (!jf) { std::cerr << "[FxGui] cannot read job file: " << jobPath << std::endl; return 1; }
     std::string data((std::istreambuf_iterator<char>(jf)), std::istreambuf_iterator<char>());
@@ -1705,6 +1715,7 @@ static int fxGuiParseJob(const std::string& jobPath, std::string& path, std::str
     path = memberString(job, "path", "");
     name = memberString(job, "name", "");
     shm = memberString(job, "shm", "");
+    presetB64 = memberString(job, "preset_b64", "");
     if (path.empty()) { std::cerr << "[FxGui] job missing path" << std::endl; return 1; }
     return 0;
 }
@@ -1746,9 +1757,15 @@ static int fxGuiCreateWindow(const std::string& name, bool offscreen,
 // 3. Load the plugin + attach the editor (SEH-guarded — plugin GUI code may
 //    crash). Slow — runs on the pump thread in server mode, after HTTP is up.
 //    Returns 0 ok, 2 plugin load or editor attach failure.
-static int fxGuiLoadAttach(Vst3Fx* fx, const std::string& path, const std::string& name, HWND hwnd) {
+static int fxGuiLoadAttach(Vst3Fx* fx, const std::string& path, const std::string& name, HWND hwnd, const std::string& presetB64) {
     // Fixed 44.1k/512 — GUI only, no audio processed here.
     if (!fx->load(path, 44100.0, 512)) { std::cerr << "[FxGui] plugin load failed: " << path << std::endl; return 2; }
+    // Khôi phục preset GUI capture cuối (hide/show mất settings bug): áp
+    // preset NGAY SAU load — trước attach editor để GUI hiện đúng cài đặt.
+    if (!presetB64.empty() && !fx->applyPreset(presetB64))
+        std::cerr << "[FxGui] preset apply FAILED (default kept): " << path << std::endl;
+    else if (!presetB64.empty())
+        std::cerr << "[FxGui] preset applied: " << path << std::endl;
     if (!fxGuiAttachSafe(fx, hwnd)) {
         std::cerr << "[FxGui] editor attach failed for " << path << std::endl;
         DestroyWindow(hwnd);
@@ -1761,13 +1778,13 @@ static int fxGuiLoadAttach(Vst3Fx* fx, const std::string& path, const std::strin
 // Combined setup (legacy open mode): parse + load + window + attach, in order.
 static int fxGuiSetup(const std::string& jobPath, Vst3Fx* fx, HWND* hwndOut,
                       bool offscreen, LONG_PTR userData, std::string& shmOut) {
-    std::string path, name;
-    int rc = fxGuiParseJob(jobPath, path, name, shmOut);
+    std::string path, name, presetB64;
+    int rc = fxGuiParseJob(jobPath, path, name, shmOut, presetB64);
     if (rc) return rc;
     if (!fx->load(path, 44100.0, 512)) { std::cerr << "[FxGui] plugin load failed: " << path << std::endl; return 2; }
     rc = fxGuiCreateWindow(name, offscreen, userData, hwndOut);
     if (rc) return rc;
-    return fxGuiLoadAttach(fx, path, name, *hwndOut);
+    return fxGuiLoadAttach(fx, path, name, *hwndOut, presetB64);
 }
 
 int run_open_fx_gui(const std::string& jobPath) {
@@ -1815,8 +1832,8 @@ int run_fx_gui_server(const std::string& jobPath) {
     // server — SF_FXGUI_PORT prints immediately. The slow VST load + editor
     // attach is deferred to the pump thread (onStarted), so plugins.py stops
     // blocking on a multi-second plugin load (startup speed issue).
-    std::string path, name, shm;
-    int rc = fxGuiParseJob(jobPath, path, name, shm);
+    std::string path, name, shm, presetB64;
+    int rc = fxGuiParseJob(jobPath, path, name, shm, presetB64);
     if (rc) return rc;
     rc = fxGuiCreateWindow(name, /*offscreen=*/true, 0, &hwnd);
     if (rc) return rc;
@@ -1826,7 +1843,7 @@ int run_fx_gui_server(const std::string& jobPath) {
 
     int loadRc = 0;
     const int srv = fxGuiServerLoop(hwnd, [&]() {
-        loadRc = fxGuiLoadAttach(&fx, path, name, hwnd);
+        loadRc = fxGuiLoadAttach(&fx, path, name, hwnd, presetB64);
         if (loadRc == 0) fxGuiStartFeederThread(&fx, hwnd);  // after load+attach only
         if (loadRc != 0) PostMessageA(hwnd, WM_CLOSE, 0, 0);  // exit; port already printed
     });