Gemini 2.5 Flash

gemini-2.5-flash is now used by default!

Ref: https://blog.google/products/gemini/gemini-2-5-model-family-expands/

Other improvements:

• Support extra_body, reasoning_effort and seed params
• Implement tools handling
• Support web search
• Support gemma-... models
• Support gemini-... embeddings models
• Misc. enhancements

Full Changelog: gemini-2.0-flash-thinking-exp...gemini-2.5-flash