chore: add brain MCP server alongside supervisor

The brain MCP at koala:30330 hosts the brain_* and session_log tools
formerly on supervisor. Supervisor stays connected during the
transition; its skill workers and the brain duplication will be
removed in a later plan.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.mcp.json

@@ -3,6 +3,10 @@
     "supervisor": {
       "type": "http",
       "url": "http://koala:30320/mcp"
+    },
+    "brain": {
+      "type": "http",
+      "url": "http://koala:30330/mcp"
     }
   }
 }