Rename sanity-plugin → sanity (#1236)

Developer requested slug change from sanity-plugin to sanity.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.claude-plugin/marketplace.json

@@ -1193,7 +1193,7 @@
       }
     },
     {
-      "name": "sanity-plugin",
+      "name": "sanity",
       "description": "Sanity content platform integration with MCP server, agent skills, and slash commands. Query and author content, build and optimize GROQ queries, design schemas, and set up Visual Editing.",
       "category": "development",
       "author": {