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-req/req-commands-plugin/.claude-plugin/plugin.json

@@ -0,0 +1,8 @@
+{
+  "name": "req-commands-plugin",
+  "description": "需求命令详细参考。含撰写命令（new/draft/edit/check/split/history/compare）和流程命令（submit/review/phase/next/deploy/done）。",
+  "version": "2.0.0",
+  "author": {
+    "name": "qiudl"
+  }
+}