LLMAssistantAggregator: preserve non-ASCII characters in JSON output

[surapuramakhil]

Add ensure_ascii=False to json.dumps() calls for tool call arguments and function call results to prevent unnecessary unicode escaping.

Please describe the changes in your PR. If it is addressing an issue, please reference that as well.

solves #3535

[Copilot]

Pull request overview

This PR fixes an issue where non-ASCII characters (e.g., Japanese, Chinese, etc.) were being unnecessarily escaped to Unicode sequences in LLM context, making it difficult for LLMs to understand conversations in non-English languages. The fix adds ensure_ascii=False parameter to json.dumps() calls to preserve the original character encoding.

Changes:

• Added ensure_ascii=False to json.dumps() for function call arguments serialization
• Added ensure_ascii=False to json.dumps() for function call result serialization

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[markbackman]

LGTM! Nice catch.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
...t/processors/aggregators/llm_response_universal.py	79.68% <100.00%> (ø)

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