Python: Record actual served model from Azure OpenAI (#5910)

* Record actual served model as response model for Azure OpenAI

* Formatting

* Fix tests

* Fix pipeline error

* Comments

* Address review: surface served model via ChatResponse.model

Apply blocking review feedback from PR #5910:

- Use ChatResponse.model / ChatResponseUpdate.model as the source of truth
  for the Azure x-ms-served-model header value, instead of stashing it in
  additional_properties and overriding it again in observability.
  Observability already reads response.model; the chat client now overwrites
  it post-parse when the served-model header is present. Empirically the
  Azure Responses API returns the deployment alias in body.model and the
  actual snapshot (e.g. gpt-5-nano-2025-08-07) in this header.

- Move the AZURE_OPENAI_SERVED_MODEL_HEADER constant out of observability.py
  and into RawOpenAIChatClient (as the SERVED_MODEL_HEADER ClassVar). The
  header is Azure-OpenAI-Responses-API-specific so observability does not
  need to know about it.

- Revert the streaming text_format path to client.responses.stream(...) and
  drop the _pydantic_model_to_text_format_param helper. That helper imported
  from openai.lib._parsing._responses (a private SDK path) and the swap to
  responses.create(stream=True) dropped client-side output_parsed for
  structured-output streaming. The streaming-with-text_format path is the
  only one that does not surface the served-model header - documented inline.

- Wrap the raw streaming responses in async with so the underlying socket
  closes deterministically (continuation_token retrieve + create paths).

- Fix the empty-string / whitespace-only header at the source by stripping
  in _extract_served_model and returning None when nothing remains.

- Revert unrelated formatting-only churn in _skills.py and test_mcp.py.

- Update unit tests to assert against chat_response.model / update.model
  and add an aggregated streaming assertion plus a pin that the
  streaming-with-text_format path does not get the header.

Verified end-to-end against Azure OpenAI Responses API: deployment alias
gpt-5-nano now reports gpt-5-nano-2025-08-07 as ChatResponse.model in both
the non-streaming and streaming paths.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix: preserve streaming structured output finalization

Agent-Logs-Url: https://github.com/microsoft/agent-framework/sessions/f62076ef-558d-49e8-8fe2-f38d527c9639

Co-authored-by: eavanvalkenburg <13749212+eavanvalkenburg@users.noreply.github.com>

* refactor: name streaming response finalizer

Agent-Logs-Url: https://github.com/microsoft/agent-framework/sessions/f62076ef-558d-49e8-8fe2-f38d527c9639

Co-authored-by: eavanvalkenburg <13749212+eavanvalkenburg@users.noreply.github.com>

* fix: capture streaming response format after prepare

Agent-Logs-Url: https://github.com/microsoft/agent-framework/sessions/f62076ef-558d-49e8-8fe2-f38d527c9639

Co-authored-by: eavanvalkenburg <13749212+eavanvalkenburg@users.noreply.github.com>

* refactor: clarify streaming response format capture

Agent-Logs-Url: https://github.com/microsoft/agent-framework/sessions/f62076ef-558d-49e8-8fe2-f38d527c9639

Co-authored-by: eavanvalkenburg <13749212+eavanvalkenburg@users.noreply.github.com>

* test: use public API for streaming structured output

Agent-Logs-Url: https://github.com/microsoft/agent-framework/sessions/f62076ef-558d-49e8-8fe2-f38d527c9639

Co-authored-by: eavanvalkenburg <13749212+eavanvalkenburg@users.noreply.github.com>

* Inline the served-model header override at its two call sites

The `_apply_served_model_header` helper was a 1-line wrapper around
`_extract_served_model`. Inlining the `if served_model is not None: ...`
matches the pattern already used in the streaming paths and folds the
explanatory docstring onto `_extract_served_model` (which is now the
single place that knows about the header).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Eduard van Valkenburg <eavanvalkenburg@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: eavanvalkenburg <13749212+eavanvalkenburg@users.noreply.github.com>

python/packages/foundry/tests/foundry/test_foundry_chat_client.py

@@ -86,12 +86,28 @@ def _with_foundry_debug() -> Any:
     return decorator
 
 
+def _as_raw(mock_response: MagicMock) -> MagicMock:
+    """Wrap ``mock_response`` so it looks like an OpenAI ``with_raw_response`` wrapper.
+
+    The chat client now calls ``responses.with_raw_response.{create,parse}`` and then
+    ``.parse()`` on the returned wrapper to get the actual response payload, plus
+    ``.headers`` to surface the ``x-ms-served-model`` Azure header.
+    """
+    mock_response.parse = MagicMock(return_value=mock_response)
+    mock_response.headers = {}
+    return mock_response
+
+
 def _make_mock_openai_client() -> MagicMock:
     client = MagicMock()
     client.default_headers = {}
     client.responses = MagicMock()
     client.responses.create = AsyncMock()
     client.responses.parse = AsyncMock()
+    client.responses.with_raw_response = MagicMock()
+    client.responses.with_raw_response.create = AsyncMock()
+    client.responses.with_raw_response.parse = AsyncMock()
+    client.responses.with_raw_response.retrieve = AsyncMock()
     client.files = MagicMock()
     client.files.create = AsyncMock()
     client.files.delete = AsyncMock()
@@ -470,7 +486,7 @@ async def test_content_filter_exception() -> None:
         body={"error": {"code": "content_filter", "message": "Content filter error"}},
     )
     mock_error.code = "content_filter"
-    client.client.responses.create.side_effect = mock_error
+    client.client.responses.with_raw_response.create.side_effect = mock_error
 
     with pytest.raises(OpenAIContentFilterException) as exc_info:
         await client.get_response(messages=[Message(role="user", contents=["Test message"])])
@@ -494,7 +510,7 @@ async def test_response_format_parse_path() -> None:
     mock_parsed_response.usage = None
     mock_parsed_response.finish_reason = None
     mock_parsed_response.conversation = None
-    client.client.responses.parse = AsyncMock(return_value=mock_parsed_response)
+    client.client.responses.with_raw_response.parse = AsyncMock(return_value=_as_raw(mock_parsed_response))
 
     response = await client.get_response(
         messages=[Message(role="user", contents=["Test message"])],
@@ -522,7 +538,7 @@ async def test_response_format_parse_path_with_conversation_id() -> None:
     mock_parsed_response.finish_reason = None
     mock_parsed_response.conversation = MagicMock()
     mock_parsed_response.conversation.id = "conversation_456"
-    client.client.responses.parse = AsyncMock(return_value=mock_parsed_response)
+    client.client.responses.with_raw_response.parse = AsyncMock(return_value=_as_raw(mock_parsed_response))
 
     response = await client.get_response(
         messages=[Message(role="user", contents=["Test message"])],
@@ -562,7 +578,7 @@ async def test_response_format_dict_parse_path() -> None:
     mock_message_item.type = "message"
     mock_message_item.content = [mock_message_content]
     mock_response.output = [mock_message_item]
-    client.client.responses.create = AsyncMock(return_value=mock_response)
+    client.client.responses.with_raw_response.create = AsyncMock(return_value=_as_raw(mock_response))
 
     response = await client.get_response(
         messages=[Message(role="user", contents=["Test message"])],
@@ -587,7 +603,7 @@ async def test_bad_request_error_non_content_filter() -> None:
         body={"error": {"code": "invalid_request", "message": "Invalid request"}},
     )
     mock_error.code = "invalid_request"
-    client.client.responses.parse = AsyncMock(side_effect=mock_error)
+    client.client.responses.with_raw_response.parse = AsyncMock(side_effect=mock_error)
 
     with pytest.raises(ChatClientException) as exc_info:
         await client.get_response(