refactor: separate provider capability policy

README.md

@@ -131,6 +131,7 @@ npm run build
 | GET | `/api/stories/{story_id}` | 故事详情 |
 | DELETE | `/api/stories/{story_id}` | 删除故事 |
 | GET/POST/PUT/DELETE | `/admin/providers` | Provider 管理，需开启管理后台 |
+| GET | `/admin/providers/capabilities` | Provider 能力分层说明，需开启管理后台 |
 
 ## 文档入口
 
@@ -138,6 +139,7 @@ npm run build
 - `docs/product/unified-generation-workflow-prd.md`：统一生成工作流 PRD
 - `docs/planning/week-1-execution-backlog.md`：短期执行 backlog
 - `docs/technical/memory-system-dev.md`：记忆系统技术说明
+- `docs/technical/provider-routing.md`：Provider 能力与路由策略说明
 
 ## 当前取舍