[BREAKING] Python: Standardize orchestration outputs as list of ChatMessage. Allow agent as group chat manager. (#2291)

* Standardize orchestration outputs as list of chatmessage. Add chat options to group chat prompt manager

* refactor group chat

* Improve group chat manager

* README Update

* Cleanup

* Add comment

* More cleanup

* Standardize termination condition for group chat

* Improvements on termination logic

* Fix tests

* Fix new line

* PR feedback

* Update ChatKit based on OpenAI type change

* Raise error if response format is not expected type

* Only one starting executor required. Add tests.

* Add magentic start executor test

python/samples/semantic-kernel-migration/orchestrations/group_chat.py

@@ -233,8 +233,8 @@ async def run_agent_framework_example(task: str) -> str:
 
     workflow = (
         GroupChatBuilder()
-        .set_prompt_based_manager(
-            chat_client=AzureOpenAIChatClient(credential=credential),
+        .set_manager(
+            manager=AzureOpenAIChatClient(credential=credential).create_agent(),
             display_name="Coordinator",
         )
         .participants(researcher=researcher, planner=planner)
@@ -245,7 +245,12 @@ async def run_agent_framework_example(task: str) -> str:
     async for event in workflow.run_stream(task):
         if isinstance(event, WorkflowOutputEvent):
             data = event.data
-            final_response = data.text or "" if isinstance(data, ChatMessage) else str(data)
+            if isinstance(data, list) and len(data) > 0:
+                # Get the final message from the conversation
+                final_message = data[-1]
+                final_response = final_message.text or "" if isinstance(final_message, ChatMessage) else str(data)
+            else:
+                final_response = str(data)
     return final_response