fix: 修复研究助手首屏滚动与欢迎区布局

frontend/src/ai/ChatPanel.tsx

@@ -10,7 +10,7 @@ import {
   IconPlus,
   IconChevronRight,
 } from "@douyinfe/semi-icons";
-import { contextLabel, contextReferences, researchPrompts } from "./workspace";
+import { contextLabel, contextReferences } from "./workspace";
 import { chatTransport } from "./transport";
 import { runLabels } from "./types";
 import type {
@@ -58,7 +58,7 @@ export function ChatPanel({
   const [loading, setLoading] = useState(false);
   const root = useRef<HTMLElement>(null);
   const input = useRef<HTMLDivElement>(null);
-  const bottom = useRef<HTMLDivElement>(null);
+  const messagesViewport = useRef<HTMLDivElement>(null);
   const previousFocus = useRef<HTMLElement | null>(null);
   const seenChanges = useRef(new Set<string>());
   const current = useRef({ conversationId, context });
@@ -206,7 +206,7 @@ export function ChatPanel({
     const editor = input.current?.querySelector<HTMLElement>(
       '[contenteditable="true"]',
     );
-    if (editor) editor.focus();
+    if (editor) editor.focus({ preventScroll: true });
     else
       root.current
         ?.querySelector<HTMLButtonElement>('button[aria-label="收起研究助手"]')
@@ -226,7 +226,11 @@ export function ChatPanel({
     };
   }, [open]);
   useEffect(() => {
-    if (open) bottom.current?.scrollIntoView({ block: "nearest" });
+    if (!open || !messagesViewport.current) return;
+    // Scroll only the message region; empty conversations always start at the welcome.
+    messagesViewport.current.scrollTop = chat.messages.length
+      ? messagesViewport.current.scrollHeight
+      : 0;
   }, [chat.messages, open]);
 
   async function createConversation() {
@@ -409,7 +413,12 @@ export function ChatPanel({
         />
       )}
       {failure && <Banner type="danger" description={failure} />}
-      <div className="ai-messages" aria-live="polite" aria-busy={streaming}>
+      <div
+        ref={messagesViewport}
+        className="ai-messages"
+        aria-live="polite"
+        aria-busy={streaming}
+      >
         {loading && <Spin />}
         {!chat.messages.length && (
           <div className="ai-empty">
@@ -428,7 +437,9 @@ export function ChatPanel({
                 开始新会话
               </Button>
             )}
-            <span>修改和任务操作会先展示预览，确认后执行。</span>
+            <p className="ai-empty-note">
+              修改和任务操作会先展示预览，确认后执行。
+            </p>
           </div>
         )}
         <AssistantDialogue
@@ -460,7 +471,6 @@ export function ChatPanel({
             )}
           </div>
         )}
-        <div ref={bottom} />
       </div>
       <footer className="ai-composer" ref={input}>
         <div className="ai-context">{contextLabel(context)}</div>
@@ -477,14 +487,6 @@ export function ChatPanel({
           busy={!!activeRun || streaming}
           onSubmit={() => void send()}
           onStop={activeRun ? () => void stop() : undefined}
-          prompts={researchPrompts(context)}
-          hint={
-            context.page === "datasets"
-              ? context.unsaved_field_selection
-                ? "字段选择尚未保存；请先保存为固定研究输入。未保存备注不会发送。"
-                : "引用随当前页面更新，未保存备注不会发送。"
-              : "引用随当前页面更新。修改和任务操作会先展示预览，确认后执行。"
-          }
         />
       </footer>
     </aside>