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/check-plan.md

@@ -337,7 +337,7 @@ Exit code is the contract that makes `check` usable in an agent loop.
 11. **Reference generator** — `scripts/generate-reference.ts` renders the
     `known.ts` catalog to markdown. Canonical output `docs/reference.md`
     (versioned, testable); `--out` can target the skill copy at
-    `~/.agents/skills/tttk-authoring/reference.md`. Add `npm run
+    `.agents/skills/tttk-authoring/reference.md`. Add `npm run
     gen:reference`.
 12. **Drift guard** — a test that greps `customElement("md-*")` call sites
     under `src/components` and asserts each appears in `known.ts` (and vice
@@ -363,7 +363,7 @@ Exit code is the contract that makes `check` usable in an agent loop.
 - Update `docs/cli.md`: replace the `compile` section with `check`; document
   codes, `--json`, exit codes.
 - Update `README.md`.
-- Update `~/.agents/skills/tttk-authoring/SKILL.md`: the verification step
+- Update `.agents/skills/tttk-authoring/SKILL.md`: the verification step
   becomes **`npx tttk check ./content`**, and the workflow becomes
   write → check → fix. Remove the "compile is a no-op stub" note. Cross-link
   the code catalog (`reference.md`) with the diagnostic codes.

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 |

docs/skill-reference-plan.md

@@ -10,6 +10,10 @@ skill's `reference.md` is now generated and byte-identical to
 `docs/reference.md`, with the extra content moved to `layout.md`, `yaml-tag.md`,
 `csv.md`, and `markdown.md`.
 
+The skill is now **owned by the repo** at `.agents/skills/tttk-authoring/` and
+activated by symlinking `~/.agents/skills/tttk-authoring` to it (see
+`docs/development.md` § Agent skills).
+
 ## 1. Goal
 
 Make the `tttk-authoring` skill's `reference.md` a **generated** file — the same
@@ -19,10 +23,10 @@ hand-maintained element list, and no content lost in the swap.
 
 ## 2. Current state
 
-The skill (`~/.agents/skills/tttk-authoring/`) has a hand-written
-`reference.md` (~465 lines) and `SKILL.md`. The repo now generates
-`docs/reference.md` from `src/cli/validate/known.ts` via `npm run
-gen:reference`.
+The skill (originally `~/.agents/skills/tttk-authoring/`, now
+`.agents/skills/tttk-authoring/`) had a hand-written `reference.md` (~465 lines)
+and `SKILL.md`. The repo generates `docs/reference.md` from
+`src/cli/validate/known.ts` via `npm run gen:reference`.
 
 What the generated doc already covers:
 
@@ -109,7 +113,7 @@ generator exists to prevent.
 `package.json`:
 
 - `gen:reference` — unchanged (writes `docs/reference.md`).
-- `gen:skill-reference` — `gen:reference -- --out ~/.agents/skills/tttk-authoring/reference.md`.
+- `gen:skill-reference` — `gen:reference -- --out .agents/skills/tttk-authoring/reference.md`.
 
 ## 6. New skill file outlines
 
@@ -156,9 +160,10 @@ generator exists to prevent.
   checklist and a manual diff before deleting the old file.
 - **`known.ts` bloat.** Keep `details` to one paragraph per element; long-form
   material belongs in the companion files.
-- **Skill path portability.** `~` expansion in the generator; the skill lives
-  outside the repo, so the drift guard cannot cover it — document that
-  `gen:skill-reference` is the refresh command.
+- **Skill path portability.** The skill now lives in the repo, so
+  `gen:skill-reference` writes to a stable path; `~` expansion in `--out`
+  remains for ad-hoc targets. Activation is a symlink, which is environment
+  setup rather than repo state — documented in `docs/development.md`.
 - **Two references.** `docs/reference.md` and the skill copy are both generated
   from `known.ts`; they must be regenerated together. Note this in
   `docs/check-plan.md` §9.