- Define _NO_TEMPERATURE_MODEL_KEYWORDS constant and omit temperature=0 on initial request
- Omit thinkingConfig in _thinking_extra_body for flash-lite models
- Unconditionally strip rejected sampling params and extra_body thinkingConfig on BadRequestError (handling Gemini 400 INVALID_ARGUMENT without named details)
- Add comprehensive unit tests in test_llm_client_gemini.py