chore(skill): Own tttk-authoring in the repo

Move the skill to .agents/skills/tttk-authoring and point gen:skill-reference at it. Activate it by symlinking ~/.agents/skills/tttk-authoring to the in-repo copy.

Extend the reference drift guard to cover the skill copy now that it is versioned, and document activation in docs/development.md.

docs/development.md

@@ -60,6 +60,9 @@ tttk/
 │   ├── styles.css              # 样式
 │   ├── index.html              # HTML 模板
 │   └── global.d.ts             # 类型声明
+├── .agents/
+│   └── skills/
+│       └── tttk-authoring/     # 随项目维护的 agent skill（见下文）
 ├── bin/
 │   └── cli/                    # CLI 二进制文件
 ├── content/                    # 示例内容
@@ -71,6 +74,29 @@ tttk/
 └── jest.config.js
 ```
 
+## Agent skills
+
+`tttk-authoring` skill 由本项目维护，源码位于
+`.agents/skills/tttk-authoring/`。要让 agent 加载它，把全局 skill 目录
+链接到仓库内的副本：
+
+```bash
+# Windows（无需管理员权限的目录联接）
+cmd //c mklink /J %USERPROFILE%\.agents\skills\tttk-authoring "%CD%\.agents\skills\tttk-authoring"
+
+# macOS / Linux
+ln -s "$PWD/.agents/skills/tttk-authoring" ~/.agents/skills/tttk-authoring
+```
+
+`reference.md` 由 `known.ts` 生成，不要手改：
+
+```bash
+npm run gen:skill-reference
+```
+
+其余文件（`SKILL.md`、`yaml-tag.md`、`csv.md`、`layout.md`、`markdown.md`）
+为手写内容。
+
 ## 技术栈
 
 | 类别 | 技术 |