refactor: 删除 session-plugin，Claude Code 已内置会话管理

删除 skills-workflow/ 目录（已清空）。44 → 43 插件。

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

.claude-plugin/marketplace.json

@@ -470,19 +470,6 @@
       ],
       "strict": false
     },
-    {
-      "name": "session-plugin",
-      "source": "./skills-workflow/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",
-      "category": "workflow",
-      "keywords": [
-        "session",
-        "workflow",
-        "productivity"
-      ],
-      "strict": false
-    },
     {
       "name": "coolbuy-legacy-plugin",
       "source": "./skills-projects/coolbuy-legacy-plugin",