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-test-gate-plugin/.claude-plugin/plugin.json

@@ -0,0 +1,8 @@
+{
+  "name": "req-test-gate-plugin",
+  "description": "测试与质量门禁制度。覆盖需求级测试(Gates 1-5，含前后端联调+视觉验证)、部署级验证(Deploy Gates)、持续回归(Regression)。",
+  "version": "1.0.0",
+  "author": {
+    "name": "qiudl"
+  }
+}