AzureChatOpenAI Reasoning Summary not extracted properly

### Submission checklist - [x] This is a bug, not a usage question. - [x] I added a clear and descriptive title that summarizes this issue. - [x] I used the GitHub search to find a similar question and didn't find it. - [x] I am sure that this is a bug in LangChain rather than my code. - [x] The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package). - [x] This is not related to the langchain-community package. - [x] I posted a self-contained, minimal, reproducible example. A maintainer can copy it and run it AS IS. ### Package (Required) - [ ] langchain - [x] langchain-openai - [ ] langchain-anthropic - [ ] langchain-classic - [ ] langchain-core - [ ] langchain-model-profiles - [ ] langchain-tests - [ ] langchain-text-splitters - [ ] langchain-chroma - [ ] langchain-deepseek - [ ] langchain-exa - [ ] langchain-fireworks - [ ] langchain-groq - [ ] langchain-huggingface - [ ] langchain-mistralai - [ ] langchain-nomic - [ ] langchain-ollama - [ ] langchain-openrouter - [ ] langchain-perplexity - [ ] langchain-qdrant - [ ] langchain-xai - [ ] Other / not sure / general ### Related Issues / PRs https://github.com/langchain-ai/langgraph/issues/5447 ### Reproduction Steps / Example Code (Python) ```python """ Minimal repro: host-shaped Responses API reasoning item (summary=[], content has reasoning_text). Run: uv run python repro_reasoning_summary.py Expected after fix: AIMessage reasoning block has non-empty summary (summary_text entries). Observed before fix: summary stays [] while raw reasoning_text remains under content. """ from __future__ import annotations from openai.types.responses import ResponseOutputMessage, ResponseReasoningItem from openai.types.responses.response import Response from openai.types.responses.response_output_text import ResponseOutputText from langchain_openai.chat_models.base import _construct_lc_result_from_responses_api def main() -> None: response = Response( id="resp_r…