[tool] fix: support non-ascii characters in search results

[Necolizer]

What does this PR do?

A small change from json.dumps({"result": final_result}) to json.dumps({"result": final_result}, ensure_ascii=False), supporting customized search engines that return docs containing non-ascii characters (e.g., CJK characters).

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[gemini-code-assist]

Code Review

This pull request addresses an issue with handling non-ASCII characters in search results by adding ensure_ascii=False to json.dumps. The change is a good step, but it's incomplete. I've pointed out that other json.dumps calls in the same function should also be updated for consistent behavior, especially for error messages which might contain non-ASCII characters. Applying this fix consistently will prevent potential encoding issues in error paths.

[gemini-code-assist]

While this change correctly handles non-ASCII characters for successful search results, the fix is incomplete. Other json.dumps calls within this function should also include ensure_ascii=False to handle non-ASCII characters consistently across all execution paths.

Error messages, in particular, can contain non-ASCII characters from exception details (e.g., file paths). Without this flag, they will be escaped, leading to inconsistent JSON output depending on whether the search was successful or resulted in an error.

Please consider updating the calls on lines 205 and 235 where error_msg is used. For full consistency, it would be best to apply this to all json.dumps calls in this function that create the result_text, including those on lines 201, 229, and 240.