feat(client): adopt an asynchronous Tokio runtime for the client frontend

crates/irtt-client/tests/managed_control.rs

@@ -197,3 +197,25 @@ fn concurrent_submission_and_stop_or_seal_never_lose_an_accepted_receipt() {
         .expect("every accepted concurrent submission must receive a terminal disposition");
     });
 }
+
+// Joining an isolated worker must leave the caller's executor free to stop it.
+#[test]
+fn async_worker_join_allows_concurrent_stop_and_preserves_final_status() {
+    let owner = BlockingManagedClient::start(config(), vec![]).unwrap();
+    let handle = owner.handle();
+    tokio::runtime::Builder::new_current_thread()
+        .enable_all()
+        .build()
+        .unwrap()
+        .block_on(async {
+            let joined = owner.join_async();
+            let stop = async { handle.stop().await };
+            let (outcome, ()) =
+                tokio::time::timeout(Duration::from_secs(2), async { tokio::join!(joined, stop) })
+                    .await
+                    .expect("async join must allow stop on the caller's executor");
+            let outcome = outcome.unwrap();
+            assert_eq!(outcome.end_reason, ManagedEndReason::StopRequested);
+            assert_eq!(handle.status().final_outcome.as_deref(), Some(&outcome));
+        });
+}