chore(lesson-preparation): V4 lint + tsc 零错误验证

重构 anchor-migration-banner：使用 key-based remount + lazy initial state 避免 setState in effect，符合 V4 react-hooks/set-state-in-effect 规则。

验证：tsc --noEmit 0 错误；lint 中 V4 引入的错误已全部修复。剩余 6 个 lint 错误为预存无关模块问题（exams/use-exam-preview-tasks react-hooks/refs 3 个、template-picker V5-9 set-state-in-effect 1 个），13 个 warnings 均为预存代码（schedule-dialog、unread-message-badge 等），按计划要求已有的无关模块错误需记录但不要求修复。

src/modules/lesson-preparation/components/anchor-migration-banner.tsx

@@ -1,28 +1,44 @@
 "use client";
 
-import { useState, useEffect } from "react";
+import { useState } from "react";
 import { useTranslations } from "next-intl";
 import { useLessonPlanEditor } from "../hooks/use-lesson-plan-editor";
+import type { LessonPlanDocument } from "../types";
 
 /**
  * V4：v3 锚点失效提示 banner。
  * 当文档含旧锚点（invalid: true 或含 start/end 字段）且未 dismiss 时显示。
  * dismiss 状态记录到 localStorage（按 planId）。
+ *
+ * 通过 key={planId} 实现 planId 变化时重新挂载内部组件，
+ * 从而使用 lazy initial state 读取 localStorage，避免在 effect 中 setState。
  */
 export function AnchorMigrationBanner() {
-  const t = useTranslations("lessonPreparation");
   const doc = useLessonPlanEditor((s) => s.doc);
   const planId = useLessonPlanEditor((s) => s.planId);
-  const [dismissed, setDismissed] = useState(false);
 
-  useEffect(() => {
-    if (planId) {
-      const stored = localStorage.getItem(`lp-legacy-anchor-dismissed-${planId}`);
-      setDismissed(stored === "true");
-    } else {
-      setDismissed(false);
-    }
-  }, [planId]);
+  return (
+    <BannerContent
+      key={planId || "no-plan"}
+      doc={doc}
+      planId={planId}
+    />
+  );
+}
+
+function BannerContent({
+  doc,
+  planId,
+}: {
+  doc: LessonPlanDocument;
+  planId: string;
+}) {
+  const t = useTranslations("lessonPreparation");
+  const [dismissed, setDismissed] = useState<boolean>(() => {
+    if (typeof window === "undefined") return false;
+    if (!planId) return false;
+    return localStorage.getItem(`lp-legacy-anchor-dismissed-${planId}`) === "true";
+  });
 
   // 检测是否有旧锚点（invalid: true 或含 start/end 字段）
   const hasLegacyAnchors = doc.anchors.some(