Gemini thinking_level support

[nahoj]

Hi. I implemented support for the thinking_level parameter which replaces thinking_budget for "Gemini 3 models and onwards" in the Google pipeline. Would you be interested in a PR?

[owndev]

Thanks for the suggestion. I implemented it myself to support thinking budgets and thinking levels.

[nahoj]

Nice, I checked it out. I wish the 2 values could be set dynamically as "Advanced params" like include_thoughts is. thinking_level could be set from the existing reasoning_effort parameter which I'd say is the same notion.

[nahoj]

I don't know if you noticed, setting a default thinking_budget=-1 renders older models that don't support thinking (eg 2.0 Flash) inoperative by default; one has to set the valve to 0 for them to work.

This is just a note, I don't mind myself as I don't use them.