fix: improve handling of OpenAI responses and simplify MCP response wrapping

src/app.py

@@ -37,10 +37,12 @@ def handle_user_input():
                 response = st.session_state.client.get_chat_response(st.session_state.messages)
 
                 # Handle both MCP and standard OpenAI responses
-                if hasattr(response, "__iter__"):
+                # Check if it's NOT a dict (assuming stream is not a dict)
+                if not isinstance(response, dict):
                     # Standard OpenAI streaming response
                     for chunk in response:
-                        if chunk.choices[0].delta.content:
+                        # Ensure chunk has choices and delta before accessing
+                        if chunk.choices and chunk.choices[0].delta and chunk.choices[0].delta.content:
                             full_response += chunk.choices[0].delta.content
                             response_placeholder.markdown(full_response + "▌")
                 else: