feat(appd): include app_id in LaunchAck response

ipc.rs: LaunchAck gains app_id: String field so callers receive the
app identifier alongside the session handle in a single response.

main.rs: dispatch::LaunchApp constructs LaunchAck { session_id, app_id }
using the app_id that was already in scope.
Tests updated: dispatch_launch_returns_ack now asserts app_id value;
dispatch_terminate_known_returns_stopped and
dispatch_query_app_state_returns_starting use .. to ignore app_id.

crates/weft-appd/src/ipc.rs

@@ -21,6 +21,7 @@ pub struct SessionInfo {
 pub enum Response {
     LaunchAck {
         session_id: u64,
+        app_id: String,
     },
     AppReady {
         session_id: u64,
@@ -98,11 +99,17 @@ mod tests {
 
     #[test]
     fn response_msgpack_roundtrip() {
-        let resp = Response::LaunchAck { session_id: 7 };
+        let resp = Response::LaunchAck {
+            session_id: 7,
+            app_id: "com.example.app".into(),
+        };
         let bytes = rmp_serde::to_vec(&resp).unwrap();
         let decoded: Response = rmp_serde::from_slice(&bytes).unwrap();
         match decoded {
-            Response::LaunchAck { session_id } => assert_eq!(session_id, 7),
+            Response::LaunchAck { session_id, app_id } => {
+                assert_eq!(session_id, 7);
+                assert_eq!(app_id, "com.example.app");
+            }
             _ => panic!("wrong variant"),
         }
     }

crates/weft-appd/src/main.rs

@@ -215,7 +215,7 @@ pub(crate) async fn dispatch(req: Request, registry: &Registry) -> Response {
                     tracing::warn!(session_id, error = %e, "runtime supervisor error");
                 }
             });
-            Response::LaunchAck { session_id }
+            Response::LaunchAck { session_id, app_id }
         }
         Request::TerminateApp { session_id } => {
             let found = registry.lock().await.terminate(session_id);
@@ -274,7 +274,13 @@ mod tests {
         )
         .await;
         match resp {
-            Response::LaunchAck { session_id } => assert!(session_id > 0),
+            Response::LaunchAck {
+                session_id,
+                ref app_id,
+            } => {
+                assert!(session_id > 0);
+                assert_eq!(app_id, "com.test.app");
+            }
             _ => panic!("expected LaunchAck"),
         }
     }
@@ -291,7 +297,7 @@ mod tests {
         )
         .await;
         let session_id = match ack {
-            Response::LaunchAck { session_id } => session_id,
+            Response::LaunchAck { session_id, .. } => session_id,
             _ => panic!("expected LaunchAck"),
         };
         let resp = dispatch(Request::TerminateApp { session_id }, &reg).await;
@@ -354,7 +360,7 @@ mod tests {
         )
         .await;
         let session_id = match ack {
-            Response::LaunchAck { session_id } => session_id,
+            Response::LaunchAck { session_id, .. } => session_id,
             _ => panic!(),
         };
         let resp = dispatch(Request::QueryAppState { session_id }, &reg).await;