feat: 添加 Analytics 分析功能（行为追踪、错误码、协议更新）

docs/protocols/models/todo.md

@@ -4,6 +4,18 @@
 
 Defines the backend/frontend data contract for `/api/v1/todos`.
 
+## Endpoints
+
+| Method | Path | Description |
+|---|---|---|
+| POST | `/api/v1/todos` | Create todo |
+| GET | `/api/v1/todos` | List todos (supports status/priority filter) |
+| GET | `/api/v1/todos/{todo_id}` | Get todo detail |
+| PATCH | `/api/v1/todos/reorder` | Batch reorder todos |
+| PATCH | `/api/v1/todos/{todo_id}` | Update todo |
+| POST | `/api/v1/todos/{todo_id}/complete` | Mark todo completed |
+| DELETE | `/api/v1/todos/{todo_id}` | Delete todo |
+
 ## Field Definitions
 
 - `id`: string (UUID)
@@ -31,6 +43,24 @@ Defines the backend/frontend data contract for `/api/v1/todos`.
 - optional: `title`, `description`, `priority`, `order`, `status`, `schedule_item_ids`
 - `order` is interpreted inside the todo's final `priority` quadrant.
 
+### List Todos (`GET /api/v1/todos`)
+
+- query `status`: `pending | done | canceled` (optional)
+- query `priority`: integer in `[1, 4]` (optional)
+
+### Reorder Todos (`PATCH /api/v1/todos/reorder`)
+
+- body: `{ items: Array<{ id, priority, order }> }`
+- each item requires:
+  - `id`: UUID
+  - `priority`: integer in `[1, 4]`
+  - `order`: integer `>= 0`
+
+### Complete Todo (`POST /api/v1/todos/{todo_id}/complete`)
+
+- body: `{}`
+- effect: sets todo status to `done` and updates `completed_at`
+
 ## Ordering Rules
 
 - Todo list API returns items sorted by `priority ASC`, then `order ASC`.