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-workflow/session-plugin/.claude-plugin/plugin.json

@@ -0,0 +1,8 @@
+{
+  "name": "session-plugin",
+  "description": "Manage Claude Code sessions — save, reload, read, and search saved conversations. Triggers on /session commands or when user mentions saving session, reloading session, finding previous conversations, or continuing previous work.",
+  "version": "1.0.0",
+  "author": {
+    "name": "qiudl"
+  }
+}