Fix Stop button: await ci.exit() so emulator process fully terminates before navigation, prevent stale audio

frontend/src/pages/Play.svelte

@@ -64,14 +64,19 @@
     booting = false;
   }
 
-  function stopEmulator() {
+  async function stopEmulator() {
-    if (dosCI) {
+    // Save reference then null it so the unmount cleanup doesn't double-try
-      try { dosCI.exit(); } catch (_) {}
+    const ci = dosCI;
     dosCI = null;
+
+    // Properly stop the emulator
+    if (ci) {
+      try { await ci.exit(); } catch (_) {}
     }
     if (dosContainer) {
       dosContainer.innerHTML = "";
     }
+
     running = false;
     push(`/game/${game.id}`);
   }