fix(core): Support of 'reasoning' type in 'convert_to_openai_messages'

[keenborder786]

• Description: Simple change to make sure 'reasoning' type is supported when Converting AI Message to Dict for OpenAI Format. Followed the following doc: https://platform.openai.com/docs/guides/reasoning
• Issue: convert_to_openai_messages does not handle the ChatOpenAI response/v1 format #32679

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1 Skipped Deployment

Project	Deployment	Preview	Comments	Updated (UTC)
langchain	Ignored	Preview		Sep 27, 2025 1:03pm

[keenborder786]

@mdrxy

[codspeed-hq]

CodSpeed WallTime Performance Report

Merging #33050 will not alter performance

_{Comparing keenborder786:fix/reasoning_parameter (475b5bf) with master (9863023)¹}

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

Summary

✅ 13 untouched

Footnotes

1. No successful run was found on master (54ea620) during the generation of this report, so 9863023 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[keenborder786]

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