阶段3（下）：RAG、向量数据库专题；接入 BOSS直聘调研（research/、岗位对照和延伸技术栈）；新增 cs 领域和 12 个技术栈骨架；面试题全部补齐追问并加入校验

schema/frontmatter.schema.json

@@ -8,8 +8,8 @@
   "properties": {
     "id": {"type": "string", "pattern": "^[a-z0-9]+(\\.[a-z0-9-]+)+$", "description": "全局唯一、稳定不变的内容 ID"},
     "title": {"type": "string"},
-    "type": {"enum": ["index", "lesson", "scenario", "interview", "project", "week"]},
-    "domain": {"enum": ["backend", "devops", "python", "ai", "frontend", "cross", "plan"]},
+    "type": {"enum": ["index", "lesson", "scenario", "interview", "project", "week", "research"]},
+    "domain": {"enum": ["backend", "devops", "python", "ai", "frontend", "cs", "cross", "plan"]},
     "stack": {"type": "array", "items": {"type": "string"}, "description": "技术栈标识，与 topics/<domain>/<stack>/ 目录名一致"},
     "tags": {"type": "array", "items": {"type": "string"}},
     "level": {"enum": ["basic", "intermediate", "advanced"]},