feat(portal-shell): 学生域全页面迁移与规范合规修复

- 学生域 32 页全量迁移(含作答/自动保存/提交/诊断)

- 补齐 4 个 MSW mock 缺口,修 diagnostic case 名

- 修 4 处 Tailwind 任意值;新增共享组件与路由

apps/portal-shell/src/features/teacher/ai/services/usage-tracker.ts

@@ -0,0 +1,132 @@
+/**
+ * portal-shell 适配：trackEvent/EventName 在客户端微前端不存在，
+ * 服务端埋点由 BFF 负责；此处保留为 no-op 占位以保持类型契约。
+ */
+type EventName = string;
+const trackEvent = async (_event: {
+  event: EventName;
+  userId: string;
+  targetType?: string;
+  properties?: Record<string, unknown>;
+}): Promise<void> => {
+  /* no-op: portal-shell client-side stub */
+};
+/**
+ * portal-shell 适配：data-access/recordAiEvent 在客户端微前端不存在，
+ * 由 BFF 维护事件存储；此处保留为 no-op 占位。
+ */
+const recordAiEvent = (_event: {
+  userId: string;
+  capability: string;
+  success: boolean;
+  durationMs: number;
+  timestamp: number;
+  errorMessage?: string;
+}): void => {
+  /* no-op: portal-shell client-side stub */
+};
+
+export type AiUsageEvent = {
+  userId: string;
+  capability:
+    | "chat"
+    | "similar_question"
+    | "grading_assist"
+    | "lesson_content"
+    | "question_variant"
+    | "weakness_analysis"
+    | "child_summary"
+    | "study_path"
+    | "explain_error";
+  providerId?: string;
+  model?: string;
+  success: boolean;
+  durationMs: number;
+  tokenUsage?: number;
+  errorMessage?: string;
+};
+
+const AI_EVENT_MAP: Record<AiUsageEvent["capability"], EventName> = {
+  chat: "ai.chat",
+  similar_question: "ai.similar_question",
+  grading_assist: "ai.grading_assist",
+  lesson_content: "ai.lesson_content",
+  question_variant: "ai.question_variant",
+  weakness_analysis: "ai.weakness_analysis",
+  child_summary: "ai.child_summary",
+  study_path: "ai.study_path",
+  explain_error: "ai.explain_error",
+};
+
+/**
+ * AI 使用埋点
+ *
+ * 记录每次 AI 调用的元数据，用于监控、成本分析与异常排查。
+ * 同时写入 data-access 层的内存事件存储（供管理员仪表盘聚合查询）。
+ * 非阻塞，失败不影响主流程。
+ */
+export const trackAiUsage = (event: AiUsageEvent): void => {
+  const eventName = AI_EVENT_MAP[event.capability];
+
+  // 写入 data-access 层（供 getAiUsageStats 聚合）
+  recordAiEvent({
+    userId: event.userId,
+    capability: event.capability,
+    success: event.success,
+    durationMs: event.durationMs,
+    timestamp: Date.now(),
+    errorMessage: event.errorMessage,
+  });
+
+  // 写入全局 trackEvent（供外部监控系统）
+  void trackEvent({
+    event: eventName,
+    userId: event.userId,
+    targetType: event.capability,
+    properties: {
+      providerId: event.providerId,
+      model: event.model,
+      success: event.success,
+      durationMs: event.durationMs,
+      tokenUsage: event.tokenUsage,
+      errorMessage: event.errorMessage,
+    },
+  }).catch(() => {
+    // 静默失败：埋点不应影响业务流程
+  });
+};
+
+/**
+ * 测量 AI 调用耗时并自动埋点
+ */
+export const withAiTracking = async <T>(
+  userId: string,
+  capability: AiUsageEvent["capability"],
+  providerId: string | undefined,
+  fn: () => Promise<{ result: T; model?: string; tokenUsage?: number }>,
+): Promise<T> => {
+  const start = Date.now();
+  try {
+    const { result, model, tokenUsage } = await fn();
+    trackAiUsage({
+      userId,
+      capability,
+      providerId,
+      model,
+      success: true,
+      durationMs: Date.now() - start,
+      tokenUsage,
+    });
+    return result;
+  } catch (error) {
+    trackAiUsage({
+      userId,
+      capability,
+      providerId,
+      success: false,
+      durationMs: Date.now() - start,
+      errorMessage: error instanceof Error ? error.message : String(error),
+    });
+    throw error;
+  }
+};