feat: open native VST FX GUI from mastering panel + FX rack (bridge --open-fx-gui)

native_bridge/include/RenderFxJob.h

@@ -36,4 +36,12 @@ int run_render_fx_job(const std::string& jobPath, const std::string& inPath,
 // crashes the module loader is skipped, not fatal).
 int run_scan_dir(const std::string& dirPath);
 
+// GUI mode (Mastering/FX Rack → "mở VST GUI"): `daw_vst_bridge --open-fx-gui
+// <job.json>` loads ONE VST3 effect plugin, opens its native editor window and
+// runs a message loop until the user closes the window (WM_DESTROY), then
+// detaches the view and exits 0. job.json: { "path": "...", "name": "..." }.
+// Windows only. Exit codes: 0 ok, 1 job/argument error, 2 plugin load or
+// editor attach failure.
+int run_open_fx_gui(const std::string& jobPath);
+
 #endif // RENDER_FX_JOB_H