Clear stale frontend run state

frontend/app/app/assistant.tsx

@@ -71,6 +71,11 @@ export const Assistant = () => {
 	const replaySession = useCallback(
 		(sessionId: string, repository: ExportedMessageRepository) => {
 			writeActiveSessionId(sessionId);
+			// 后端已经落盘/结束后，用回放结果接管当前会话。
+			// 先取消本地仍挂起的 assistant-ui run，避免 UI 残留“运行中”且无法停止。
+			if (runtime.thread.getState().isRunning) {
+				runtime.thread.cancelRun();
+			}
 			runtime.thread.import(repository);
 		},
 		[runtime],

frontend/app/components/assistant-ui/thread.tsx

@@ -908,6 +908,7 @@ const ComposerWorkspaceStatus: FC<{ sessionId: string | null }> = ({
 };
 
 const ComposerAction: FC = () => {
+	const aui = useAui();
 	const runtimeRunning = useAuiState((s) => s.thread.isRunning);
 	const replayedRun = useReplayedRunState();
 	const currentSessionId = useCurrentThreadSessionId({
@@ -955,6 +956,8 @@ const ComposerAction: FC = () => {
 						void cancelLatestRun(cancelSessionId, replayedRun.runId)
 							.catch(() => undefined)
 							.finally(() => {
+								// 后端可能已经 idle；无论取消接口是否真的命中 run，都清理本地残留运行态。
+								aui.thread().cancelRun();
 								window.setTimeout(() => setRuntimeCancelling(false), 1200);
 							});
 					}}