Python: Fix OpenAI Responses streaming to propagate created_at from final response.completed event (#5382)

* Fix streaming response losing created_at from response.completed event (#5347)

The streaming path in _parse_chunk_from_openai did not extract created_at
from the response.completed event, unlike the non-streaming path in
_parse_responses_response. This caused durabletask persistence warnings
when created_at was None.

Extract created_at in the response.completed case and pass it to the
returned ChatResponseUpdate.

Also fix pre-existing pyright errors for optional orjson import in sample
files.

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

* Fix orjson import suppression to use pyright instead of mypy (#5347)

Replace `# type: ignore[import-not-found]` with
`# pyright: ignore[reportMissingImports]` on optional orjson imports
in conversation sample files, matching the repo's Pyright strict
configuration.

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

---------

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

python/samples/02-agents/conversations/file_history_provider.py

@@ -21,7 +21,7 @@ from dotenv import load_dotenv
 from pydantic import Field
 
 try:
-    import orjson
+    import orjson  # pyright: ignore[reportMissingImports]
 except ImportError:
     orjson = None
 

python/samples/02-agents/conversations/file_history_provider_conversation_persistence.py

@@ -22,7 +22,7 @@ from dotenv import load_dotenv
 from pydantic import Field
 
 try:
-    import orjson
+    import orjson  # pyright: ignore[reportMissingImports]
 except ImportError:
     orjson = None