fix(chat): follow active response at bottom

frontend/src/components/rectification-agentic-chat.tsx

@@ -83,7 +83,7 @@ export function AgenticRectificationChat(props: AgenticRectificationChatProps) {
   const [acceptingTime, setAcceptingTime] = useState<string | null>(null);
   const [suggestions, setSuggestions] = useState<string[]>([]);
   const composer = useRef<HTMLTextAreaElement>(null);
-  const conversationEnd = useRef<HTMLDivElement>(null);
+  const conversation = useRef<HTMLElement>(null);
   const keyCounter = useRef(0);
   const openingStarted = useRef(false);
 
@@ -93,12 +93,14 @@ export function AgenticRectificationChat(props: AgenticRectificationChatProps) {
   }, [onPendingChange]);
 
   useEffect(() => {
+    const container = conversation.current;
+    if (!container) return;
     const reduceMotion = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
-    conversationEnd.current?.scrollIntoView({
+    container.scrollTo({
+      top: container.scrollHeight,
       behavior: busy || reduceMotion ? "auto" : "smooth",
-      block: "end",
     });
-  }, [busy, error, messages.length, savedTime]);
+  }, [busy, error, messages, savedTime]);
 
   const send = useCallback(async (request: AgenticRectificationRequest, showUserMessage = true) => {
     const trimmed = request.action === "message" ? request.message.trim() : "";
@@ -301,7 +303,7 @@ export function AgenticRectificationChat(props: AgenticRectificationChatProps) {
 
   return (
     <>
-      <section className="conversation" aria-label="生时校正对话" aria-busy={busy}>
+      <section ref={conversation} className="conversation" aria-label="生时校正对话" aria-busy={busy}>
         <div className="message-list" aria-live="polite">
           {messages.map((message) => <ChatMessageRow key={message.renderKey} message={message} />)}
           {candidateResult?.selectionAllowed && candidateResult.candidates.length > 0 && (
@@ -344,7 +346,6 @@ export function AgenticRectificationChat(props: AgenticRectificationChatProps) {
             </p>
           )}
           {error && <p className="error-message" role="alert">{error}</p>}
-          <div ref={conversationEnd} />
         </div>
       </section>