feat(appd): broadcast AppState::Stopped when supervised process exits

runtime.rs: after the child exits (natural exit or abort), supervise()
now broadcasts AppState { session_id, state: Stopped } in the same
lock scope as set_state. WebSocket clients receive the notification
without needing to poll QueryAppState or call TerminateApp.

crates/weft-appd/src/runtime.rs

@@ -75,10 +75,14 @@ pub(crate) async fn supervise(
         }
     }
 
-    registry
-        .lock()
-        .await
-        .set_state(session_id, AppStateKind::Stopped);
+    {
+        let mut reg = registry.lock().await;
+        reg.set_state(session_id, AppStateKind::Stopped);
+        let _ = reg.broadcast().send(Response::AppState {
+            session_id,
+            state: AppStateKind::Stopped,
+        });
+    }
 
     Ok(())
 }