feat(skills): 独立维护智能体生命周期操作说明 (#90)

## 中文

### 变更
- 新增 `clone-agent` 内置 Skill，覆盖私有数据复制和团队分发边界
- 将 Smart routing、reasoning、头像和确认流程迁入 action-specific Skills
- 修正 `update-agent` 与当前 ManageAgent 白名单的漂移
- 保持所有市场 Skill 按需加载，并加入 builtin 清单

### 验证
- `uv run --quiet scripts/i18n/test_validate_i18n.py`
- `uv run --quiet scripts/i18n/validate-i18n.py`
- `uv run --quiet scripts/i18n/translate.py --check`
- 公共信息边界检查通过

## English

### Changes
- Add the built-in `clone-agent` Skill for private-data copy and
team-distribution boundaries
- Move Smart routing, reasoning, avatar, and confirmation workflows into
action-specific Skills
- Align `update-agent` with the current ManageAgent configuration
whitelist
- Keep every marketplace Skill on-demand and add the new Skill to the
built-in manifest

### Verification
- `uv run --quiet scripts/i18n/test_validate_i18n.py`
- `uv run --quiet scripts/i18n/validate-i18n.py`
- `uv run --quiet scripts/i18n/translate.py --check`
- Public information boundary review passed

builtin-skills.json

@@ -1,5 +1,6 @@
 {
   "skills": [
+    "clone-agent",
     "code-intelligence",
     "configuring-compute",
     "create-agent",