fix: bound vector store file polling

[he-yufeng]

Fixes #3097

Summary

• add an optional max_wait_seconds bound to vector_stores.files.poll()
• thread the same bound through sync/async create_and_poll() and upload_and_poll()
• raise TimeoutError instead of waiting forever when a vector store file stays in_progress

Why

upload_and_poll() currently waits until the vector store file reaches a terminal state. If the backend leaves the vector store file in in_progress indefinitely, the helper never returns and the caller has no SDK-level escape hatch. The new argument keeps the default behavior unchanged, while letting callers opt into a bounded wait.

Validation

• PYTHONPATH=src python -m pytest tests/api_resources/vector_stores/test_files.py::TestFiles::test_poll_timeout tests/api_resources/vector_stores/test_files.py::TestAsyncFiles::test_poll_timeout -q

• PYTHONPATH=src python -m pytest tests/api_resources/vector_stores/test_files.py::test_create_and_poll_method_in_sync tests/api_resources/vector_stores/test_files.py::test_upload_and_poll_method_in_sync -q

• PYTHONPATH=src python -m ruff check src/openai/resources/vector_stores/files.py tests/api_resources/vector_stores/test_files.py

• python -m compileall -q src/openai/resources/vector_stores/files.py tests/api_resources/vector_stores/test_files.py

• git diff --check

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