feat(portal-shell): questions + textbooks 模块 3 页迁移（教师域 §9.1 B2）
§9.1 line 630-631 教师域：
- /shell/teacher/questions (列表，1 页)
- /shell/teacher/textbooks + /shell/teacher/textbooks/[id] (列表+详情，2 页)
契约：🟡 混合
- question(id) ✅ 真实单查（schema 第 775-778 行确认）
- textbook(id) ✅ 真实单查
- 列表查询 ❌ schema 无 → MSW 兜底 + @contract-pending
- textbookChapters(textbookId) ❌ schema 无 → MSW 兜底
新增文件：
- src/lib/api/questions.ts (5 hooks)
- src/lib/api/textbooks.ts (5 hooks)
- src/lib/api/operations/{questions,textbooks}.graphql.ts (10 documents)
- src/features/teacher/questions/ (clients + transformations + tests)
- src/features/teacher/textbooks/ (clients + transformations + tests)
- src/app/shell/teacher/{questions,textbooks}/ (3 page.tsx + 2 loading + 2 error)
修改文件：
- src/lib/api/teacher.ts + operations/teacher.graphql.ts
→ 重命名 legacy widget API 以解决命名冲突：
Question → QuestionBankItem
Textbook → LegacyTextbook
Chapter → LegacyChapter
TextbookFilter → LegacyTextbookFilter
useTextbooks → useLegacyTextbooks
GET_QUESTIONS_DOC → GET_QUESTION_BANK_DOC
GET_TEXTBOOKS_DOC → GET_LEGACY_TEXTBOOKS_DOC
- src/widgets/teacher/{question-bank,textbook-manager}/index.tsx
→ 更新引用为重命名后的 legacy API
- src/mocks/graphql-data.ts
→ 添加 questions/textbooks mock + GetQuestionBank/GetLegacyTextbooks handler
- src/messages/{zh-CN,en}.json (questions + textbooks i18n)
- src/lib/api/{index,operations/index}.ts (导出 questions + textbooks)
- src/shared/lib/route-permissions.ts (questions + textbooks 路由权限)
- scripts/check-page-count.ts (baseline 37 → 40)
DoD 验收（§11.3 11 项）：
- typecheck 0 errors
- lint 0 errors
- vitest 469 tests passed (新增 64 tests)
- lint:tokens 0 errors
- check:pages 40 PASS
- route-permissions 已声明
- 三态齐备
- @contract-pending + MSW 兜底
- i18n zh-CN + en 同步
关联：ARCHITECTURE.md §5.3 / §5.4 / §5.5 / §9.1 / §10 P2 / §11.3 / §11.4
契约工单：docs/architecture/issues/contracts/core-edu_contract.md
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