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

app/api/v1/plugins.py

@@ -701,12 +701,12 @@ async def open_fx_gui(req: FxGuiRequest, current_user: dict = Depends(get_curren
     (exit 0). Không spawn 2 lần cho cùng plugin đang mở (tránh trùng GUI).
     """
     enforce_password_changed(current_user)
-    from app.core.native_render import find_bridge_exe
-    exe = find_bridge_exe()
+    from app.core.native_render import find_fx_bridge_exe
+    exe = find_fx_bridge_exe()
     if not exe:
         raise HTTPException(
             status_code=409,
-            detail="Không tìm thấy bridge native (daw_vst_bridge.exe). "
+            detail="Không tìm thấy bridge native (fx_vst_bridge.exe). "
                    "Hãy chạy bản desktop đã build đầy đủ.",
         )
     plugin_path = (req.path or "").strip()

app/core/native_render.py

@@ -19,33 +19,47 @@ from fastapi import HTTPException
 from app.config import settings
 
 BRIDGE_EXE = "daw_vst_bridge.exe" if os.name == "nt" else "daw_vst_bridge"
+FX_BRIDGE_EXE = "fx_vst_bridge.exe" if os.name == "nt" else "fx_vst_bridge"
 
 
-def find_bridge_exe() -> str:
-    """Đường dẫn bridge exe: env SF_BRIDGE_PATH → bundle (frozen) → install/ (dev)."""
-    env = os.getenv("SF_BRIDGE_PATH", "").strip()
+def find_bridge_exe(exe_name=BRIDGE_EXE, env_key="SF_BRIDGE_PATH") -> str:
+    """Đường dẫn bridge exe: env <env_key> → bundle (frozen) → src-tauri/binaries → install/ (dev)."""
+    env = os.getenv(env_key, "").strip()
     if env and os.path.isfile(env):
         return env
+    # Tauri externalBin renames sidecars → <name>-x86_64-pc-windows-msvc.exe.
+    sidecar = exe_name[:-4] + "-x86_64-pc-windows-msvc.exe" if exe_name.lower().endswith(".exe") else exe_name
     cands = []
     if getattr(sys, "frozen", False):
         root = getattr(sys, "_MEIPASS", "")
         if root:
-            cands += [os.path.join(root, "binaries", BRIDGE_EXE),
-                      os.path.join(root, BRIDGE_EXE)]
+            cands += [os.path.join(root, "binaries", exe_name),
+                      os.path.join(root, "binaries", sidecar),
+                      os.path.join(root, exe_name),
+                      os.path.join(root, sidecar)]
         # PyInstaller onedir: daw_engine.exe nam <app_root>/daw_engine/, bridge
         # sidecar nam canh app root (khong trong _MEIPASS) - tim ca exe_dir.
         exe_dir = os.path.dirname(os.path.abspath(sys.executable))
-        cands += [os.path.join(exe_dir, "binaries", BRIDGE_EXE),
-                  os.path.join(exe_dir, BRIDGE_EXE),
-                  os.path.join(os.path.dirname(exe_dir), "binaries", BRIDGE_EXE),
-                  os.path.join(os.path.dirname(exe_dir), BRIDGE_EXE)]
-    cands.append(os.path.join(settings.BASE_DIR, "install", BRIDGE_EXE))
+        cands += [os.path.join(exe_dir, "binaries", exe_name),
+                  os.path.join(exe_dir, "binaries", sidecar),
+                  os.path.join(exe_dir, exe_name),
+                  os.path.join(exe_dir, sidecar),
+                  os.path.join(os.path.dirname(exe_dir), "binaries", exe_name),
+                  os.path.join(os.path.dirname(exe_dir), "binaries", sidecar),
+                  os.path.join(os.path.dirname(exe_dir), exe_name),
+                  os.path.join(os.path.dirname(exe_dir), sidecar)]
+    # Canonical build output (build_native_bridge.ps1) + legacy install/ (dev).
+    cands.append(os.path.join(settings.BASE_DIR, "src-tauri", "binaries", sidecar))
+    cands.append(os.path.join(settings.BASE_DIR, "install", exe_name))
     for p in cands:
         if p and os.path.isfile(p):
             return p
     return ""
 
 
+def find_fx_bridge_exe() -> str:
+    """Đường dẫn FX bridge (fx_vst_bridge.exe): SF_FX_BRIDGE_PATH → bundle → install/."""
+    return find_bridge_exe(FX_BRIDGE_EXE, "SF_FX_BRIDGE_PATH")
 def normalize_audio_peak(audio, target_db=0.0):
     """Scale audio (numpy array, peak) về target_db nếu vượt; giữ nguyên nếu dưới.
 
@@ -209,18 +223,18 @@ def render_fx_chain(input_wav, fx_chain, sample_rate, out_path=None) -> str:
     out_path; lỗi → HTTPException (501 thiếu bridge, 404 plugin lạ, 500 render).
     """
     from app.core.vst_engine import resolve_plugin_path
-    exe = find_bridge_exe()
+    exe = find_fx_bridge_exe()
     if not exe:
         raise HTTPException(
             status_code=501,
-            detail="native_bridge không khả dụng — đặt SF_BRIDGE_PATH hoặc cài daw_vst_bridge",
+            detail="native_bridge không khả dụng — đặt SF_FX_BRIDGE_PATH hoặc cài fx_vst_bridge",
         )
     slots = []
     for fx in fx_chain or []:
         typ = fx.get("type")
         if typ == "vst3":
             p = (fx.get("path") or "").strip()
-            resolved = p if os.path.isfile(p) else resolve_plugin_path(p, ".vst3")
+            resolved = p if os.path.exists(p) else resolve_plugin_path(p, ".vst3")
             if not resolved:
                 raise HTTPException(
                     status_code=404,

app/core/vst_engine.py

@@ -481,8 +481,8 @@ class PluginManager:
         """
         if not refresh and self._fx_scan_cache is not None:
             return self._fx_scan_cache
-        from app.core.native_render import find_bridge_exe
-        exe = find_bridge_exe()
+        from app.core.native_render import find_fx_bridge_exe
+        exe = find_fx_bridge_exe()
         results = []
         if exe:
             dirs = [d for d in [self.vst_dir] + self.extra_vst_dirs
@@ -629,7 +629,8 @@ def resolve_plugin_path(name_or_path: str, ext: str = "") -> str:
         dirs = list(_load_user_plugin_dirs()) or []
     except Exception:
         pass
-    dirs += [settings.VST_DIR, settings.SOUNDFONT_DIR]
+    from app.config import settings as _st
+    dirs += [_st.VST_DIR, _st.SOUNDFONT_DIR]
     for base_dir in dirs:
         if not os.path.isdir(base_dir):
             continue