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/doubao-voice-plugin/.claude-plugin/plugin.json

@@ -0,0 +1,14 @@
+{
+  "name": "doubao-voice-plugin",
+  "description": "Doubao (豆包) Voice API integration for TTS and ASR",
+  "version": "1.0.0",
+  "author": {
+    "name": "qiudl"
+  },
+  "skills": [
+    {
+      "name": "doubao-voice",
+      "path": "./skills/SKILL.md"
+    }
+  ]
+}