Fix session cancel and new task routing

frontend/app/app/assistant.tsx

@@ -255,12 +255,15 @@ function AssistantWorkspace() {
 			setActiveSessionId(next);
 		};
 		const handleChanged = (event: Event) => {
-			const detail = (event as CustomEvent<{ sessionId?: string | null }>)
-				.detail;
-			const next =
-				detail?.sessionId ?? readSessionIdFromUrl() ?? readActiveSessionId();
+			const customEvent = event as CustomEvent<{ sessionId?: string | null }>;
+			const hasExplicitSession =
+				customEvent.detail &&
+				Object.prototype.hasOwnProperty.call(customEvent.detail, "sessionId");
+			const next = hasExplicitSession
+				? (customEvent.detail.sessionId ?? null)
+				: (readSessionIdFromUrl() ?? readActiveSessionId());
 			console.log("[active-session] event-changed", {
-				detailSessionId: detail?.sessionId,
+				detailSessionId: customEvent.detail?.sessionId,
 				next,
 			});
 			setActiveSessionId(next);

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

@@ -131,8 +131,8 @@ const ThreadListNew: FC = () => {
 			variant="outline"
 			className="aui-thread-list-new h-9 w-full justify-start gap-2 rounded-lg px-3 text-sm hover:bg-muted data-active:bg-muted"
 			onClick={() => {
-				clearActiveSessionId();
 				pushHomeUrl();
+				clearActiveSessionId();
 				clearSession();
 				window.dispatchEvent(new Event("claw-active-session-cleared"));
 			}}

frontend/app/components/assistant-ui/threadlist-sidebar.tsx

@@ -203,8 +203,8 @@ function CollapsedSidebarRail({
 				<CollapsedIconButton
 					label="新任务"
 					onClick={() => {
-						clearActiveSessionId();
 						pushHomeUrl();
+						clearActiveSessionId();
 						clearSession();
 						window.dispatchEvent(new Event("claw-active-session-cleared"));
 					}}