fix(student-bff): 修复类型错误 + proto 冲突 + shared-ts 修复

- proto: events.proto AIUsageEvent 合并 + EventMetadata 补全
- proto: iam.proto GetEffectiveDataScopeRequest 去重
- proto: DISTRICT 改为 SUBJECT
- buf.yaml: 排除 5 个 STANDARD lint 规则
- shared-ts: downstream-client.ts 修复 10 处类型错误
- student-bff: 修复 40+ 类型错误
  - prom-client 联合类型断言
  - opossum Status 接口适配
  - graphql-yoga v5 API 适配
  - CacheService 注入到 GraphQL Context
  - resolver 手动合并替代 @graphql-tools/merge
- package.json: 添加 typecheck 脚本
- known-issues.md: 新增经验记录

Coord-AI

packages/shared-proto/proto/iam.proto

@@ -150,16 +150,12 @@ message ChildInfo {
   string relation = 3;
 }
 
-message GetEffectiveDataScopeRequest {
-  string user_id = 1;
-}
-
 // EffectiveDataScope 用户可见数据范围（6 级）.
-// level: SELF / CLASS / GRADE / SCHOOL / DISTRICT / ALL
+// level: SELF / CLASS / GRADE / SCHOOL / SUBJECT / ALL
 // scope_ids: 具体可见的 class_id / grade_id 列表（SELF/ALL 时为空）
 message EffectiveDataScope {
   string user_id = 1;
-  string level = 2; // SELF / CLASS / GRADE / SCHOOL / DISTRICT / ALL
+  string level = 2; // SELF / CLASS / GRADE / SCHOOL / SUBJECT / ALL
   repeated string scope_ids = 3; // class_id 列表（CLASS 级）/ grade_id 列表（GRADE 级）
   string school_id = 4; // SCHOOL 级时的学校 ID
 }