[WIP] Fix deserialization issues for Gemini API responses

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

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This section details on the original issue you should resolve

<issue_title>sometimes Failed deserialize Gemini API responses</issue_title>
<issue_description>I haven't found out cause of this problem yet.

guess causes

• not enough struct field for deserialize
• llm problems(e.g. api limit)
  • fix: be parsable more details of api errors
  • (temp): when failing parse a response, parse response as de and print raw response.</issue_description>

<agent_instructions>pls fix</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@Uliboooo exmaple

:) ggw commit -m gemini/gemini-3-flash-preview
⠏ LLM call finished.
Error: Llm(ChatCompletion("Deserialization error: error decoding response body"))
```</body></comment_new>
</comments>