langchain-openai==1.5.2

Changes since langchain-openai==1.5.1

release(openai): 1.5.2 (#39719)
fix(openai): preserve reasoning item boundaries (#39278)
release(openai): 1.5.2a1 (#39709)
feat(openai): extract gateway metadata from response headers when available (#39706)
chore(openai): update snapshots (#39657)
fix(openai): support o-series models in get_num_tokens_from_messages (#38710)