Python: fix: include status field on function_call and function_call_output items

[LEDazzio01]

Motivation and Context

Fixes #4701.

When replaying conversation history that includes tool calls through the Responses API, the _prepare_content_for_openai method produced items that violated the API schema:

1. function_call items set "status": None unconditionally. For AG-UI client-side tools where additional_properties does not carry an explicit status, this resulted in null being sent to the API, causing a 400 Bad Request.
2. function_call_output items omitted the status field entirely, also causing API rejections.

Changes

_responses_client.py

• function_call: Resolve status from content.additional_properties when available, falling back to "completed" when absent or None.
• function_call_output: Always include "status": "completed".

test_openai_responses_client.py

Added 4 unit tests:

• test_prepare_content_function_call_defaults_status_to_completed — verifies default fallback
• test_prepare_content_function_call_preserves_explicit_status — verifies explicit status is preserved
• test_prepare_content_function_result_includes_status_completed — verifies function_call_output always has status
• test_prepare_content_function_result_none_result — verifies None result maps to empty string with status

[Copilot]

Pull request overview

Fixes serialization of tool-call history for the OpenAI Responses API by ensuring status is always present (and never null) on function_call and function_call_output items, preventing 400s when replaying conversation history (notably for AG-UI client-side tools).

Changes:

• Default function_call.status to "completed" when missing/None, while preserving an explicit status if provided.
• Always include "status": "completed" on function_call_output items.
• Add unit tests covering the status behavior for both item types (including None function result output).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
python/packages/core/agent_framework/openai/_responses_client.py	Ensures Responses-API tool-call items always include a valid status field (function_call default/preserve; function_call_output always completed).
python/packages/core/tests/openai/test_openai_responses_client.py	Adds focused unit tests validating status handling for tool-call serialization.

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[LEDazzio01]

Closing this in favor of #4704 by @ltwlf, who originally reported the issue and has a more comprehensive fix that also includes filename passthrough for media parts. Thanks for the great catch and fix, @ltwlf! 🙌