fix(web): portal the natal board peek without effect setState

Quality gate lint failed on setHeaderSlot inside useLayoutEffect, so staging never published. Pass the header mount node from a callback ref instead.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/app/page.tsx

@@ -1074,6 +1074,7 @@ export default function Home() {
   );
   const [rectificationSessionId, setRectificationSessionId] = useState<string | null>(null);
   const [rectificationCaseId, setRectificationCaseId] = useState<string | null>(null);
+  const [rectificationHeaderSlot, setRectificationHeaderSlot] = useState<HTMLElement | null>(null);
   const [rectificationPendingQuestion, setRectificationPendingQuestion] = useState<string | null>(null);
   const [rectificationLoading, setRectificationLoading] = useState(false);
   const [rectificationMutationPending, setRectificationMutationPending] = useState(false);
@@ -3566,7 +3567,7 @@ export default function Home() {
             <strong>{activeSession?.title || "新对话"}</strong>
           </div>
           <div className="chat-header-actions">
-            <div className="chat-header-rectification" data-rectification-header-slot="" />
+            <div className="chat-header-rectification" data-rectification-header-slot="" ref={setRectificationHeaderSlot} />
             <button className="credit-button" type="button" onClick={() => router.push(membershipHref("credits"))} aria-label={account ? `余额 ${account.credits} 点，会员与充值` : accountError || "读取余额中"}>
               <Sparkles className="credit-icon" aria-hidden="true" />
               <span>{account ? account.credits : "—"}</span>
@@ -3806,6 +3807,7 @@ export default function Home() {
             onStartConsultation={() => void startConsultationAfterRectification()}
             pendingConsultationQuestion={rectificationPendingQuestion}
             onRestart={() => void startNewRectification()}
+            headerSlot={rectificationHeaderSlot}
           />
         )}