fix: khong panic khi spawn engine fail (UI khong thoat) + spawn.log chan doan (path + exists) + giu SF_PARENT_PID

src-tauri/src/lib.rs

@@ -25,15 +25,35 @@ pub fn run() {
             } else {
                 engine_dir.join("daw_engine")
             };
-            let (_rx, child) = app
-                .shell()
-                .command(engine_exe)
+            // Ghi log spawn de chan doan (UI khong duoc panic/thoat — chi log)
+            let log_line = format!(
+                "spawn daw_engine: {} exists={}\n",
+                engine_exe.display(),
+                engine_exe.exists()
+            );
+            if let Some(mut f) = std::fs::OpenOptions::new()
+                .create(true)
+                .append(true)
+                .open(engine_dir.join("spawn.log"))
+                .ok()
+            {
+                use std::io::Write;
+                let _ = f.write_all(log_line.as_bytes());
+            }
+            match app.shell().command(&engine_exe)
                 .env("SF_PARENT_PID", std::process::id().to_string())
-                .spawn()
-                .expect("Failed to spawn daw_engine (onedir resource) — run build_windows.ps1 first");
-
-            app.manage(EngineProcess(Mutex::new(Some(child))));
-            println!("Python Background Engine started (localhost:8000, auto-fallback 8000-8010)");
+                .spawn() {
+                Ok((_rx, child)) => {
+                    app.manage(EngineProcess(Mutex::new(Some(child))));
+                    println!("Python Background Engine started (localhost:8000, auto-fallback 8000-8010)");
+                }
+                Err(e) => {
+                    // Khong panic: UI van mo, engine loi se hien trong UI loader
+                    // ("Khong tim thay SonicForge Engine"). Log ro de chan doan.
+                    println!("Failed to spawn daw_engine: {e}");
+                    app.manage(EngineProcess(Mutex::new(None)));
+                }
+            }
             Ok(())
         })
         .on_window_event(|window, event| {