feat(portal-shell): exams 三子页面迁移（analytics/build/edit）

§9.1 教师域 exams 模块补完（继 d066da5 列表/详情/表单后）：
- /shell/teacher/exams/[id]/analytics：详情页（图表）- 混合契约
  · 基础统计 ✅ assignmentAnalysis（data-ana 子图，schema 已就绪）
  · 扩展字段（排名/每题正确率）❌ MSW 兜底（@contract-pending）
  · 含 Summary/Distribution/QuestionAccuracy/Rankings 四区
- /shell/teacher/exams/[id]/build：工作台页（组卷）@contract-pending
  · 三栏：题库候选 / 已选题目 / 预览
  · 支持搜索/类型/难度筛选，添加/移除/上移/下移/改分
- /shell/teacher/exams/[id]/edit：工作台页（富文本试卷）@contract-pending
  · contentEditable + 工具栏（B/I/U/H1-H3/列表）
  · 右栏试卷属性面板

§11.3 DoD 11 项验收：
1. route-permissions：PREFIX 表 /shell/teacher/exams/ 已覆盖
2. 页面模板：analytics 用 DetailPageShell；build/edit 用 WorkbenchPageShell
3. 三态：loading/error/empty 均实现（workbench 用 errorNode 合并 empty）
4. lib/api hooks：useExamAnalytics/useExamBuild/useQuestionsLibrary/
   useSaveExamBuild/useExamRichEditor/useSaveExamRichContent 6 个
5. @contract-pending MSW 模式：graphql-data.ts 扩展 6 个 case
6. i18n：analytics(19 keys)+build(28 keys)+edit(13 keys) 中英对齐
7. lint：0 errors（4 warnings 在 __generated__）
8. lint:tokens：0 errors
9. notify：success/error/warning 走 @/shared/lib/notify（非 sonner 直引）
10. vitest：transformations 新增 10 函数 22 测试，全量 273/273 通过
11. typecheck：0 errors（noUncheckedIndexedAccess 安全 swap 写法）

剩余：proctoring 标注"二期 WS"按 §9.1 暂缓。

apps/portal-shell/src/messages/en.json

@@ -210,6 +210,95 @@
       "errorTitleRequired": "Please fill in exam title",
       "errorDateRequired": "Please select exam date",
       "contractPending": "Create exam contract is @contract-pending, currently backed by MSW. Will switch to real submission once backend mutation is ready."
+    },
+    "analytics": {
+      "title": "Exam Analytics",
+      "subtitle": "Exam ID: {examId}",
+      "exportCsv": "Export CSV",
+      "notFound": "No analytics data found, grading may not be complete",
+      "sectionSummary": "Summary",
+      "sectionDistribution": "Score Distribution",
+      "sectionQuestionAccuracy": "Question Accuracy",
+      "sectionRankings": "Student Rankings",
+      "summaryExpected": "Expected",
+      "summaryAttended": "Attended",
+      "summaryAvg": "Average",
+      "summaryMax": "Max",
+      "summaryMin": "Min",
+      "summaryPassRate": "Pass Rate",
+      "emptyDistribution": "No score distribution data",
+      "emptyQuestionAccuracy": "No question accuracy data",
+      "emptyRankings": "No ranking data",
+      "colOrder": "#",
+      "colQuestionTitle": "Question",
+      "colCorrectRate": "Correct Rate",
+      "colAvgScore": "Avg Score",
+      "colMaxScore": "Max Score",
+      "colRank": "Rank",
+      "colStudentNo": "Student No.",
+      "colStudentName": "Name",
+      "colTotalScore": "Total Score",
+      "colLevel": "Level"
+    },
+    "build": {
+      "title": "Build Exam",
+      "subtitle": "Current total: {total} pts · Pass score: {pass} pts",
+      "save": "Save Build",
+      "saveSuccess": "Build saved successfully",
+      "saveFailed": "Save failed: {message}",
+      "notFound": "No build data found",
+      "alreadyAdded": "This question has already been added",
+      "libraryTitle": "Question Library",
+      "searchPlaceholder": "Search question content...",
+      "filterType": "Filter by type",
+      "filterDifficulty": "Filter by difficulty",
+      "allTypes": "All types",
+      "allDifficulties": "All difficulties",
+      "typeSingle": "Single Choice",
+      "typeMultiple": "Multiple Choice",
+      "typeFill": "Fill in the Blank",
+      "typeEssay": "Essay",
+      "diffEasy": "Easy",
+      "diffMedium": "Medium",
+      "diffHard": "Hard",
+      "loadingLibrary": "Loading library...",
+      "loadLibraryFailed": "Library load failed",
+      "libraryEmpty": "No questions match the filter",
+      "libraryTotal": "{total} questions total",
+      "addToExam": "Add to exam",
+      "unitScore": "pts",
+      "selectedTitle": "Selected Questions",
+      "selectedCount": "{count} questions",
+      "selectedEmpty": "Add questions from the library on the left",
+      "scoreLabel": "Score",
+      "moveUp": "Move up",
+      "moveDown": "Move down",
+      "remove": "Remove",
+      "previewTitle": "Preview",
+      "previewTotal": "Total Score",
+      "previewBaseline": "Baseline: {baseline} pts",
+      "previewPassScore": "Pass Score",
+      "previewTypeBreakdown": "Type Breakdown"
+    },
+    "edit": {
+      "title": "Edit Exam Paper",
+      "subtitle": "Total: {total} pts · {count} questions",
+      "save": "Save Paper",
+      "saveSuccess": "Paper saved successfully",
+      "saveFailed": "Save failed: {message}",
+      "notFound": "No paper content found",
+      "propertiesTitle": "Paper Properties",
+      "propExamId": "Exam ID",
+      "propTotalScore": "Total Score",
+      "propQuestionCount": "Question Count",
+      "propUpdatedAt": "Last Updated",
+      "contractPending": "Rich text editor contract is @contract-pending, currently backed by MSW. Will switch to real data once backend is ready.",
+      "editorTitle": "Paper Content",
+      "toolbarBold": "Bold",
+      "toolbarItalic": "Italic",
+      "toolbarUnderline": "Underline",
+      "toolbarBulletList": "Bullet list",
+      "toolbarOrderedList": "Ordered list"
     }
   },
   "homework": {