优化聊天框输入聚焦逻辑，增强网络错误处理

src/components/chat/GlobalChatbox.tsx

@@ -113,6 +113,7 @@ export const GlobalChatbox: React.FC<Props> = ({ open, onClose }) => {
   const [conversationId, setConversationId] = useState<string | undefined>(undefined);
   const abortRef = useRef<AbortController | null>(null);
   const bottomRef = useRef<HTMLDivElement>(null);
+  const inputRef = useRef<HTMLInputElement | null>(null);
   const theme = useTheme();
 
   const canSend = useMemo(() => input.trim().length > 0 && !isStreaming, [input, isStreaming]);
@@ -122,6 +123,14 @@ export const GlobalChatbox: React.FC<Props> = ({ open, onClose }) => {
     bottomRef.current?.scrollIntoView({ behavior: "smooth" });
   }, [messages, isStreaming]);
 
+  useEffect(() => {
+    if (!open) return;
+    const timer = window.setTimeout(() => {
+      inputRef.current?.focus();
+    }, 0);
+    return () => window.clearTimeout(timer);
+  }, [open]);
+
   const handleSend = async () => {
     const prompt = input.trim();
     if (!prompt || isStreaming) return;
@@ -443,6 +452,7 @@ export const GlobalChatbox: React.FC<Props> = ({ open, onClose }) => {
                 }}
             >
                 <TextField
+                inputRef={inputRef}
                 value={input}
                 onChange={(e) => setInput(e.target.value)}
                 onKeyDown={(e) => {