refactor: 通用技能按类别拆分为独立目录

skills/ → skills-dev(9), skills-req(10), skills-ops(4),
skills-integration(8), skills-biz(4), skills-workflow(7)

generate-marketplace.py 改为自动扫描所有 skills-* 目录。

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

skills-integration/siyuan-to-feishu-plugin/.claude-plugin/plugin.json

@@ -0,0 +1,8 @@
+{
+  "name": "siyuan-to-feishu-plugin",
+  "description": "将思源笔记导出为 PDF 并发送到飞书群。当用户提到发送笔记、导出PDF发飞书、/siyuan send、分享到飞书相关任务时自动激活。",
+  "version": "1.0.0",
+  "author": {
+    "name": "qiudl"
+  }
+}