fix: remove SSE connection failure notice timer

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/context/ChatContext.tsx

@@ -1844,8 +1844,6 @@ export function ChatProvider({ children }: { children: ReactNode }) {
 
 		let eventSource: EventSource | null = null;
 		let reconnectTimer: ReturnType<typeof setTimeout> | null = null;
-		let sseNoticeTimer: ReturnType<typeof setTimeout> | null = null;
-		let sseNoticeShown = false;
 
 		const connect = () => {
 			if (eventSource) eventSource.close();
@@ -1869,12 +1867,6 @@ export function ChatProvider({ children }: { children: ReactNode }) {
 
 		connect();
 
-		sseNoticeTimer = setTimeout(() => {
-			if (cancelled || sseNoticeShown) return;
-			sseNoticeShown = true;
-			addSystemMessageRef.current("无法连接实时事件流，请确认 WebUI 已启动且穿透域名可访问");
-		}, 12_000);
-
 		return () => {
 			cancelled = true;
 			window.removeEventListener("resize", onResize);
@@ -1882,7 +1874,6 @@ export function ChatProvider({ children }: { children: ReactNode }) {
 			window.visualViewport?.removeEventListener("scroll", syncViewportHeight);
 			window.removeEventListener("orientationchange", syncViewportHeight);
 			if (reconnectTimer) clearTimeout(reconnectTimer);
-			if (sseNoticeTimer) clearTimeout(sseNoticeTimer);
 			eventSource?.close();
 		};
 	}, []);