refactor: 移除 metadata.version 冗余，顶层 version 为唯一来源

- 所有 SKILL.md 的版本号统一由顶层 version 字段定义
- 删除 metadata 中的冗余 version 副本
- 参考 OpenClaw 实践：version 作为顶层一等公民

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

skills/create-agent/SKILL.md

@@ -14,8 +14,7 @@ tags:
   - meta
 metadata:
   author: desirecore
-  version: 2.2.0
-  updated_at: '2026-02-27'
+  updated_at: '2026-02-28'
 market:
   icon: >-
     <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0

skills/delete-agent/SKILL.md

@@ -7,7 +7,6 @@ status: enabled
 disable-model-invocation: true
 metadata:
   author: desirecore
-  version: 2.2.0
   updated_at: '2026-02-28'
 version: 2.2.0
 tags:

skills/discover-agent/SKILL.md

@@ -12,7 +12,6 @@ tags:
   - recommendation
 metadata:
   author: desirecore
-  version: 2.2.0
   updated_at: '2026-02-28'
 market:
   icon: >-

skills/update-agent/SKILL.md

@@ -14,8 +14,7 @@ tags:
   - meta
 metadata:
   author: desirecore
-  version: 2.2.0
-  updated_at: '2026-02-27'
+  updated_at: '2026-02-28'
 market:
   icon: >-
     <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0