refactor(bridge): split fx bridge, stabilize VST3 host chain, drop old install engines

- remove diagnostic canaries from audio hot path (crackle fix) and
  stuck C5 note raw-MIDI test (Vst2Instrument::init noteOff)
- split native bridge into daw_vst_bridge (VSTi) + fx_vst_bridge (VST FX)
- VST3: processData prepare before setActive, zero input buses, accept
  both .vstpreset and bridge-state blob in RenderJob presets
- native_render/vst_engine: bridge-exe discovery + render_fx_chain + /fx-gui
- delete old install/ engine binaries (install via sidecar+resources now)
- add BUILD_LAYOUT.md, build_selfcheck, tools/ diagnostics

build/scripts/build_native_bridge.ps1

@@ -79,7 +79,7 @@ cmake -S $NB_DIR -B $BUILD_DIR -G $VS_GEN -A $VS_ARCH `
   -DCMAKE_BUILD_TYPE=Release `
   -DVCPKG_TARGET_TRIPLET=x64-windows
 if ($LASTEXITCODE -ne 0) { Write-Host "ERROR: cmake configure failed" -ForegroundColor Red; exit 1 }
-cmake --build $BUILD_DIR --config Release --target daw_vst_bridge -- /m
+cmake --build $BUILD_DIR --config Release --target daw_vst_bridge fx_vst_bridge -- /m
 if ($LASTEXITCODE -ne 0) { Write-Host "ERROR: cmake build failed" -ForegroundColor Red; exit 1 }
 
 # 6. Copy sidecar to Tauri externalBin location
@@ -89,9 +89,13 @@ New-Item -ItemType Directory -Force $BIN_DIR | Out-Null
 $EXE = Join-Path $BUILD_DIR "Release\daw_vst_bridge.exe"
 if (-not (Test-Path $EXE)) { Write-Host "ERROR: $EXE not found" -ForegroundColor Red; exit 1 }
 Copy-Item $EXE (Join-Path $BIN_DIR "daw_vst_bridge-x86_64-pc-windows-msvc.exe") -Force
+# fx_vst_bridge: VST FX host sidecar (split — see CMakeLists.txt)
+$FX_EXE = Join-Path $BUILD_DIR "Release\fx_vst_bridge.exe"
+if (-not (Test-Path $FX_EXE)) { Write-Host "ERROR: $FX_EXE not found" -ForegroundColor Red; exit 1 }
+Copy-Item $FX_EXE (Join-Path $BIN_DIR "fx_vst_bridge-x86_64-pc-windows-msvc.exe") -Force
 
-# 7. Copy fluidsynth runtime DLL next to sidecar (Tauri externalBin bundles only the exe)
-Write-Host "== [7/7] Copy libfluidsynth-3.dll =="
+# 7. Copy runtime DLLs next to sidecar (Tauri externalBin bundles only the exe)
+Write-Host "== [7/7] Copy runtime DLLs (fluidsynth + jpeg) =="
 $FS_DLL = Join-Path $BUILD_DIR "vcpkg_installed\x64-windows\bin\libfluidsynth-3.dll"
 if (-not (Test-Path $FS_DLL)) { $FS_DLL = Join-Path $VCPKG_ROOT "installed\x64-windows\bin\libfluidsynth-3.dll" }
 if (Test-Path $FS_DLL) {
@@ -101,4 +105,15 @@ if (Test-Path $FS_DLL) {
 } else {
   Write-Host "WARN: libfluidsynth-3.dll not found - bridge needs it at runtime" -ForegroundColor Yellow
 }
+# jpeg62.dll (VST3 hosting image decode; vcpkg libjpeg-turbo) - same candidates as fluidsynth
+$JPEG_DLL = Join-Path $NB_DIR "vcpkg_installed\x64-windows\bin\jpeg62.dll"
+if (-not (Test-Path $JPEG_DLL)) { $JPEG_DLL = Join-Path $BUILD_DIR "vcpkg_installed\x64-windows\bin\jpeg62.dll" }
+if (-not (Test-Path $JPEG_DLL)) { $JPEG_DLL = Join-Path $VCPKG_ROOT "packages\libjpeg-turbo_x64-windows\bin\jpeg62.dll" }
+if (Test-Path $JPEG_DLL) {
+  Copy-Item $JPEG_DLL (Join-Path $BIN_DIR "jpeg62.dll") -Force
+  Copy-Item $JPEG_DLL (Join-Path $BUILD_DIR "Release\jpeg62.dll") -Force
+  Write-Host "  jpeg62.dll copied to src-tauri\binaries"
+} else {
+  Write-Host "WARN: jpeg62.dll not found - VST3 GUIs may fail to show images" -ForegroundColor Yellow
+}
 Write-Host "== DONE: sidecar + DLL in src-tauri\binaries =="

build/scripts/build_windows.ps1

@@ -57,8 +57,8 @@ if ($LASTEXITCODE -ne 0) { Write-Host "ERROR: bridge sidecar missing" -Foregroun
 npm install -D @tauri-apps/cli
 # Frontend host: copy template -> src-tauri/ui/index.html (giu Tauri context,
 # document.write UI engine; neu thieu -> window mat __TAURI__ -> bridge chet).
-Copy-Item buildscriptsfrontend_host_index.html src-tauriuiindex.html -Force
-if (-not (Test-Path src-tauriuiindex.html)) { Write-Host "ERROR: frontend host missing" -ForegroundColor Red; exit 1 }
+Copy-Item build\scripts\index.html src-tauri\ui\index.html -Force
+if (-not (Test-Path src-tauri\ui\index.html)) { Write-Host "ERROR: frontend host missing" -ForegroundColor Red; exit 1 }
 npx tauri build
 
 Write-Host ""