docs: 工程骨架落地记录（架构 §13）与 AGENTS.md 工程一节

- 架构 §13：SK1–SK8，SK1（事件流用 Valkey stream）、SK2（测试不用 testcontainers）待确认
- api-design §10：接口实现进度
- openapi.yaml：ChecklistItem 的必填字段在同一层声明，生成的类型不再是可选
- AGENTS.md：目录结构、常用命令、编码约定、当前进度

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/architecture/openapi.yaml

@@ -2524,6 +2524,12 @@ components:
         - type: object
           required: [categories, title]
           properties:
+            categories:
+              type: array
+              minItems: 1
+              uniqueItems: true
+              items: { $ref: '#/components/schemas/Category' }
+            title: { type: string, minLength: 1, maxLength: 200 }
             citation_ids:
               type: array
               items: { $ref: '#/components/schemas/Id' }
@@ -2535,6 +2541,13 @@ components:
         - type: object
           required: [id, categories, title, importance, origin, zone, citations, edited_fields, updated_at]
           properties:
+            categories:
+              type: array
+              minItems: 1
+              uniqueItems: true
+              items: { $ref: '#/components/schemas/Category' }
+            title: { type: string, minLength: 1, maxLength: 200 }
+            importance: { $ref: '#/components/schemas/Importance' }
             id: { $ref: '#/components/schemas/Id' }
             summary:
               type: [string, 'null']