Python: Raise clear handler registration error for unresolved TypeVar annotations (#4944)

* Raise clear handler registration error for unresolved TypeVar (#4943)

Detect unresolved TypeVar in message parameter annotations during handler
registration in both _validate_handler_signature (Executor) and
_validate_function_signature (FunctionExecutor). Raises a ValueError with
an actionable message recommending @handler(input=..., output=...) or
@executor(input=..., output=...) instead of letting TypeVar leak through
to a confusing TypeCompatibilityError during workflow edge validation.

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

* Address review feedback for #4943: reorder checks and harden function executor

- Move TypeVar check before validate_workflow_context_annotation in
  _executor.py so users see the more actionable error first
- Wrap get_type_hints in try/except in _function_executor.py matching
  the defensive pattern in _executor.py
- Repurpose duplicate test to cover bounded TypeVar rejection
- Add test_function_executor_allows_concrete_types for test symmetry

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

* Narrow get_type_hints except clause and add missing tests (#4943)

- Narrow `except Exception` to `except (NameError, AttributeError, RecursionError)`
  in both _executor.py and _function_executor.py so unexpected failures in
  get_type_hints are not silently swallowed.
- Add test_handler_unresolvable_annotation_raises to test_function_executor_future.py
  exercising the except branch of get_type_hints in the function executor path.
- Add test_function_executor_rejects_bounded_typevar_in_message_annotation to
  test_function_executor.py for parity with the Executor bounded TypeVar test.

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

* Add error ordering test for TypeVar vs WorkflowContext priority (#4943)

Add test_handler_typevar_error_takes_priority_over_context_error to verify
that when a handler has both a TypeVar message and an unannotated ctx, the
TypeVar error is raised first (the more actionable issue).

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

* Python: Fix image content serialization sending null file_id to Foundry API

Omit file_id from input_image dict when not present instead of including
it as null, which Azure AI Foundry's stricter schema validation rejects.

* Python: Fix Foundry API rejecting rich content in function_call_output

Azure AI Foundry does not support list-format output in function_call_output
items. Add SUPPORTS_RICH_FUNCTION_OUTPUT flag (default True) to
RawOpenAIChatClient, set to False in RawFoundryChatClient so Foundry
falls back to string output for tool results with images/files.

Also omit file_id from input_image dicts when not set, since Foundry
rejects explicit nulls.

* Python: Surface rich tool content as user message when Foundry lacks support

When SUPPORTS_RICH_FUNCTION_OUTPUT is False, image/file items from tool
results are injected as a follow-up user message so the model can still
process the visual content via Foundry's supported user message format.

* Xfail Foundry image integration test for the meantime

---------

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

python/packages/foundry/agent_framework_foundry/_chat_client.py

@@ -124,6 +124,7 @@ class RawFoundryChatClient(  # type: ignore[misc]
     """
 
     OTEL_PROVIDER_NAME: ClassVar[str] = "azure.ai.foundry"  # type: ignore[reportIncompatibleVariableOverride, misc]
+    SUPPORTS_RICH_FUNCTION_OUTPUT: ClassVar[bool] = False  # type: ignore[reportIncompatibleVariableOverride, misc]
 
     def __init__(
         self,

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

@@ -715,6 +715,7 @@ async def test_integration_web_search() -> None:
 
 @pytest.mark.flaky
 @pytest.mark.integration
+@pytest.mark.xfail(reason="Azure AI Foundry stopped accepting array-format output in function_call_output ~2026-04-03")
 @skip_if_foundry_integration_tests_disabled
 @_with_foundry_debug()
 async def test_integration_tool_rich_content_image() -> None: