Add Agent Message Queue icon (#137)

Author: avivsinai

plugins/avivsinai/agent-message-queue/.codex-plugin/plugin.json

@@ -22,6 +22,7 @@
   ],
   "interface": {
     "displayName": "Agent Message Queue",
+    "composerIcon": "./assets/icon.png",
     "shortDescription": "File-based inter-agent messaging with co-op mode, federation, and orchestrator integrations",
     "category": "Developer Tools"
   }