refactor: 项目技能拆分到 skills-projects/

将 coolbuy (3) 和 enjoysa (2) 共 5 个项目特定技能从 skills/ 移至 skills-projects/，
保持通用技能与业务项目技能分离。

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

skills-projects/coolbuy-legacy-plugin/.claude-plugin/plugin.json

@@ -0,0 +1,8 @@
+{
+  "name": "coolbuy-legacy-plugin",
+  "description": "酷采2.0团购管理系统测试与维护。用于酷采2.0系统的功能测试、问题排查、需求验证和对比测试。",
+  "version": "1.0.0",
+  "author": {
+    "name": "qiudl"
+  }
+}