Update mongodb source to plugins/mongodb subdir (upstream restructure) (#4347)

.claude-plugin/marketplace.json

@@ -2235,9 +2235,11 @@
       "description": "Official Claude plugin for MongoDB (MCP Server + Skills). Connect to databases, explore data, manage collections, optimize queries, generate reliable code, implement best practices, develop advanced features, and more.",
       "category": "database",
       "source": {
-        "source": "url",
+        "source": "git-subdir",
         "url": "https://github.com/mongodb/agent-skills.git",
-        "sha": "be846b4deb482c22a5fb4d133d6c1e6c4a32eb08"
+        "path": "plugins/mongodb",
+        "ref": "main",
+        "sha": "b4ea8150a020b9babaddc6c271c6dc177c06a83f"
       },
       "homepage": "https://www.mongodb.com/docs/mcp-server/overview/"
     },