feat: add SSE server with agent presence system

- Add SSE transport server for remote MCP connections
- Implement API key authentication
- Add agent presence system (register_agent, list_agents)
- Add list_services tool to discover local services
- Refactor messaging for dynamic agent names

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package.json

@@ -29,6 +29,7 @@
     "@types/ws": "^8.18.1",
     "cors": "^2.8.5",
     "dotenv": "^16.4.5",
+    "eventsource": "^4.1.0",
     "express": "^4.18.2",
     "jsonwebtoken": "^9.0.2",
     "nats": "^2.19.0",