Python: [BREAKING] Simplify API: ChatAgent -> Agent, ChatMessage -> Message (#3747)

* [BREAKING] Rename ChatAgent -> Agent, ChatMessage -> Message, ChatClientProtocol -> SupportsChatGetResponse

Simplify the public API by removing redundant 'Chat' prefix from core types:
- ChatAgent -> Agent
- RawChatAgent -> RawAgent
- ChatMessage -> Message
- ChatClientProtocol -> SupportsChatGetResponse

Also renamed internal WorkflowMessage (was Message in _runner_context) to avoid collision.

No backward compatibility aliases - this is a clean breaking change.

* [BREAKING] Rename Agent chat_client parameter to client

* Fix rebase issues: WorkflowMessage references and broken markdown links

* Fix formatting and lint issues from code quality checks

* Fix import ordering in workflow sample files

* fixed rebase

* Fix test failures: use WorkflowMessage and A2AMessage after ChatMessage→Message rename

- Replace Message(data=..., source_id=...) with WorkflowMessage(...) in workflow tests
- Fix isinstance check in A2A agent to use A2AMessage instead of Message
- Fix import in test_workflow_observability.py (Message→WorkflowMessage)

* Fix lint, fmt, and sample errors after ChatMessage→Message rename

- Auto-fix 70+ ruff lint issues across samples (ChatMessage→Message refs)
- Fix HostedVectorStoreContent→Content.from_hosted_vector_store in file search sample
- Fix _normalize_messages→normalize_messages in custom agent sample
- Fix context.terminate→raise MiddlewareTermination in middleware samples
- Fix with_update_hook→with_transform_hook in override middleware sample
- Add TOptions_co import back to custom_chat_client sample
- Add noqa for FastAPI File() default in chatkit sample
- Fix B023 loop variable capture in weather agent sample

* fix: update Agent constructor calls from chat_client to client in declaration-only tool tests

* fix: add register_cleanup to devui lazy-loading proxy and type stub

* fixed tests and updated new pieces

* fix agui typevar

* fix merge errors

* fix merge conflicts

* fiux merge

* Remove unused links

---------

Co-authored-by: Evan Mattson <evan.mattson@microsoft.com>

python/samples/getting_started/tools/function_tool_with_approval.py

@@ -4,7 +4,7 @@ import asyncio
 from random import randrange
 from typing import TYPE_CHECKING, Annotated, Any
 
-from agent_framework import AgentResponse, ChatAgent, ChatMessage, tool
+from agent_framework import Agent, AgentResponse, Message, tool
 from agent_framework.openai import OpenAIResponsesClient
 
 if TYPE_CHECKING:
@@ -59,14 +59,14 @@ async def handle_approvals(query: str, agent: "SupportsAgentRun") -> AgentRespon
             )
 
             # Add the assistant message with the approval request
-            new_inputs.append(ChatMessage("assistant", [user_input_needed]))
+            new_inputs.append(Message("assistant", [user_input_needed]))
 
             # Get user approval
             user_approval = await asyncio.to_thread(input, "\nApprove function call? (y/n): ")
 
             # Add the user's approval response
             new_inputs.append(
-                ChatMessage("user", [user_input_needed.to_function_approval_response(user_approval.lower() == "y")])
+                Message("user", [user_input_needed.to_function_approval_response(user_approval.lower() == "y")])
             )
 
         # Run again with all the context
@@ -109,14 +109,14 @@ async def handle_approvals_streaming(query: str, agent: "SupportsAgentRun") -> N
                 )
 
                 # Add the assistant message with the approval request
-                new_inputs.append(ChatMessage("assistant", [user_input_needed]))
+                new_inputs.append(Message("assistant", [user_input_needed]))
 
                 # Get user approval
                 user_approval = await asyncio.to_thread(input, "\nApprove function call? (y/n): ")
 
                 # Add the user's approval response
                 new_inputs.append(
-                    ChatMessage("user", [user_input_needed.to_function_approval_response(user_approval.lower() == "y")])
+                    Message("user", [user_input_needed.to_function_approval_response(user_approval.lower() == "y")])
                 )
 
             # Update input with all the context for next iteration
@@ -127,8 +127,8 @@ async def run_weather_agent_with_approval(stream: bool) -> None:
     """Example showing AI function with approval requirement."""
     print(f"\n=== Weather Agent with Approval Required ({'Streaming' if stream else 'Non-Streaming'}) ===\n")
 
-    async with ChatAgent(
-        chat_client=OpenAIResponsesClient(),
+    async with Agent(
+        client=OpenAIResponsesClient(),
         name="WeatherAgent",
         instructions=("You are a helpful weather assistant. Use the get_weather tool to provide weather information."),
         tools=[get_weather, get_weather_detail],

python/samples/getting_started/tools/function_tool_with_approval_and_threads.py

@@ -3,7 +3,7 @@
 import asyncio
 from typing import Annotated
 
-from agent_framework import ChatAgent, ChatMessage, tool
+from agent_framework import Agent, Message, tool
 from agent_framework.azure import AzureOpenAIChatClient
 
 """
@@ -28,8 +28,8 @@ async def approval_example() -> None:
     """Example showing approval with threads."""
     print("=== Tool Approval with Thread ===\n")
 
-    agent = ChatAgent(
-        chat_client=AzureOpenAIChatClient(),
+    agent = Agent(
+        client=AzureOpenAIChatClient(),
         name="CalendarAgent",
         instructions="You are a helpful calendar assistant.",
         tools=[add_to_calendar],
@@ -55,7 +55,7 @@ async def approval_example() -> None:
 
             # Step 2: Send approval response
             approval_response = request.to_function_approval_response(approved=approved)
-            result = await agent.run(ChatMessage("user", [approval_response]), thread=thread)
+            result = await agent.run(Message("user", [approval_response]), thread=thread)
 
     print(f"Agent: {result}\n")
 
@@ -64,8 +64,8 @@ async def rejection_example() -> None:
     """Example showing rejection with threads."""
     print("=== Tool Rejection with Thread ===\n")
 
-    agent = ChatAgent(
-        chat_client=AzureOpenAIChatClient(),
+    agent = Agent(
+        client=AzureOpenAIChatClient(),
         name="CalendarAgent",
         instructions="You are a helpful calendar assistant.",
         tools=[add_to_calendar],
@@ -88,7 +88,7 @@ async def rejection_example() -> None:
 
             # Send rejection response
             rejection_response = request.to_function_approval_response(approved=False)
-            result = await agent.run(ChatMessage("user", [rejection_response]), thread=thread)
+            result = await agent.run(Message("user", [rejection_response]), thread=thread)
 
     print(f"Agent: {result}\n")