Revert to old Gradio format for HF Spaces compatibility

- Removed type="messages" parameter (not supported in HF Gradio)
- Use list of [user, bot] pairs instead of dict format
- Fixes: TypeError: Chatbot.__init__() got an unexpected keyword argument 'type'

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app.py

@@ -170,7 +170,7 @@ def chat(message, history):
 with gr.Blocks() as demo:
     gr.Markdown(f"# MedRAX2 - Medical AI Assistant\n**Device:** {device} | **Tools:** {len(tools)} loaded | **Orchestrator:** Gemini 2.0 Flash")
 
-    chatbot = gr.Chatbot(type="messages")
+    chatbot = gr.Chatbot()
     viz_output = gr.Image(label="Grounding Visualization", visible=True)
 
     msg = gr.MultimodalTextbox(
@@ -189,19 +189,11 @@ with gr.Blocks() as demo:
         else:
             text = message
 
-        # Add to chat history - use messages format for newer Gradio
+        # Add to chat history - use list of pairs format for older Gradio
         if chat_history is None:
             chat_history = []
 
-        # Check if we need messages format or list format
-        if len(chat_history) > 0 and isinstance(chat_history[0], dict):
-            # Messages format
-            chat_history.append({"role": "user", "content": text})
-            chat_history.append({"role": "assistant", "content": bot_message})
-        else:
-            # Try messages format first (for newer Gradio)
-            chat_history.append({"role": "user", "content": text})
-            chat_history.append({"role": "assistant", "content": bot_message})
+        chat_history.append([text, bot_message])
 
         return "", chat_history, viz_image