feat(ai): 新增 AI 模块并集成至备课/错题集/试卷/改题四大业务场景

- 新增 src/modules/ai 独立模块，遵循三层架构（actions → services → shared/lib/ai）
- 通过 AiClientProvider + useAiClient 实现 React Context 依赖注入，业务组件零直接 import
- 6 个 Server Actions 均调用 requirePermission() 权限校验，返回 ActionState<T>
- withAiTracking 统一埋点，覆盖 chat/similar_question/grading_assist/lesson_content/question_variant/weakness_analysis
- 集成场景：作业批改 AiGradingAssist、错题集 AiErrorBookAnalysis、备课 AiLessonContentGenerator、试卷 AiQuestionVariantGenerator
- 全量 i18n（en/zh-CN ai.json），Error Boundary + Skeleton 边界处理
- 同步架构图 004/005，新增审计报告 ai-module-audit-report.md

src/modules/lesson-preparation/components/node-edit-panel.tsx

@@ -1,11 +1,15 @@
 "use client";
 
+import { useState } from "react";
 import { useTranslations } from "next-intl";
+import { Sparkles, ChevronDown, ChevronUp } from "lucide-react";
 import { useLessonPlanEditor } from "../hooks/use-lesson-plan-editor";
 import { BlockRenderer } from "../config/block-registry";
 import { LessonPlanErrorBoundary } from "./lesson-plan-error-boundary";
 import { Button } from "@/shared/components/ui/button";
 import { Trash2, X } from "lucide-react";
+import { AiLessonContentGenerator } from "@/modules/ai/components/ai-lesson-content-generator";
+import { useAiClientOptional } from "@/modules/ai/context/ai-client-provider";
 
 interface Props {
   textbookId?: string;
@@ -15,8 +19,11 @@ interface Props {
 
 export function NodeEditPanel({ textbookId, chapterId, classes }: Props) {
   const t = useTranslations("lessonPreparation");
+  const tAi = useTranslations("ai");
   const { doc, selectedNodeId, updateNode, removeNode, selectNode } =
     useLessonPlanEditor();
+  const aiClient = useAiClientOptional();
+  const [showAiPanel, setShowAiPanel] = useState(false);
 
   const node = doc.nodes.find((n) => n.id === selectedNodeId);
 
@@ -28,15 +35,45 @@ export function NodeEditPanel({ textbookId, chapterId, classes }: Props) {
     );
   }
 
+  // 正文节点不在侧边面板编辑（直接在画布上交互）
+  if (node.type === "textbook_content") {
+    return (
+      <div className="h-full flex flex-col border-l border-outline-variant bg-surface">
+        <div className="flex items-center gap-2 px-4 py-2 border-b border-outline-variant">
+          <span className="flex-1 font-title-md text-title-md">
+            {t("editor.textbookContent")}
+          </span>
+          <Button
+            variant="ghost"
+            size="sm"
+            onClick={() => selectNode(null)}
+            aria-label={t("action.close")}
+          >
+            <X className="w-4 h-4" aria-hidden="true" />
+          </Button>
+        </div>
+        <div className="flex-1 overflow-y-auto p-4 text-sm text-on-surface-variant">
+          {t("editor.textbookContentEmpty")}
+        </div>
+      </div>
+    );
+  }
+
+  // 教学节点：通过类型守卫收窄为 LessonPlanNode
+  const lessonNode = node as import("../types").LessonPlanNode;
+
+  // 从节点标题提取主题用于 AI 内容生成
+  const aiTopic = lessonNode.title || t("editor.textbookContent");
+
   return (
     <div className="h-full flex flex-col border-l border-outline-variant bg-surface">
       {/* 面板头部 */}
       <div className="flex items-center gap-2 px-4 py-2 border-b border-outline-variant">
         <input
-          value={node.title}
-          onChange={(e) => updateNode(node.id, { title: e.target.value })}
+          value={lessonNode.title}
+          onChange={(e) => updateNode(lessonNode.id, { title: e.target.value })}
           className="flex-1 bg-transparent font-title-md text-title-md focus:outline-none"
-          aria-label={node.title}
+          aria-label={lessonNode.title}
         />
         <Button
           variant="ghost"
@@ -52,17 +89,49 @@ export function NodeEditPanel({ textbookId, chapterId, classes }: Props) {
       <div className="flex-1 overflow-y-auto p-3">
         <LessonPlanErrorBoundary>
           <BlockRenderer
-            type={node.type}
-            blockId={node.id}
-            data={node.data}
+            type={lessonNode.type}
+            blockId={lessonNode.id}
+            data={lessonNode.data}
             textbookId={textbookId}
             chapterId={chapterId}
             classes={classes}
-            onUpdate={(d) => updateNode(node.id, { data: d })}
+            onUpdate={(d) => updateNode(lessonNode.id, { data: d })}
           />
           {/* BlockRenderer 返回 null 时显示未知类型提示 */}
-          <UnknownBlockHint type={node.type} t={t} />
+          <UnknownBlockHint type={lessonNode.type} t={t} />
         </LessonPlanErrorBoundary>
+
+        {/* AI 内容生成区（可折叠） */}
+        {aiClient ? (
+          <div className="mt-4 border-t border-outline-variant pt-3">
+            <Button
+              variant="ghost"
+              size="sm"
+              className="w-full justify-between"
+              onClick={() => setShowAiPanel(!showAiPanel)}
+              aria-expanded={showAiPanel}
+            >
+              <span className="flex items-center gap-1">
+                <Sparkles className="w-3.5 h-3.5 text-primary" />
+                {tAi("lessonPrep.generateContent")}
+              </span>
+              {showAiPanel ? (
+                <ChevronUp className="w-3.5 h-3.5" />
+              ) : (
+                <ChevronDown className="w-3.5 h-3.5" />
+              )}
+            </Button>
+            {showAiPanel ? (
+              <div className="mt-2">
+                <AiLessonContentGenerator
+                  topic={aiTopic}
+                  textbookId={textbookId}
+                  chapterId={chapterId}
+                />
+              </div>
+            ) : null}
+          </div>
+        ) : null}
       </div>
 
       {/* 底部操作 */}
@@ -71,7 +140,7 @@ export function NodeEditPanel({ textbookId, chapterId, classes }: Props) {
           variant="outline"
           size="sm"
           className="text-error"
-          onClick={() => removeNode(node.id)}
+          onClick={() => removeNode(lessonNode.id)}
         >
           <Trash2 className="w-3 h-3 mr-1" aria-hidden="true" />
           {t("action.delete")}