Fix: Use deepseek/ provider directly (litellm native support, no openrouter prefix needed)

configs/frontend_agent_config.json

@@ -1,5 +1,5 @@
 {
-  "model_name": "openrouter/deepseek/deepseek-chat-v3.1",
+  "model_name": "deepseek/deepseek-chat",
   "save_sessions": true,
   "personal_trace_repo_template": "{hf_user}/ml-intern-sessions",
   "share_traces": true,