Deprecated google.generativeai package

[markmcd]

Hi team,

Mark here from the Gemini DevX team. I am trying to hunt down (and remove) significant usage of our old google-generativeai package and noticed you are using it in Shinychat.

I see #62 is removing a lot of AI handling logic, so I don't want to get in the way of any existing work, but would you be open to a PR that replaces google-generativeai use with google-genai?

I am not familiar with your users or codebase, so if you have any specific guidance or design advice, please let me know.

[cpsievert]

would you be open to a PR that replaces google-generativeai use with google-genai?

Yes, that'd be great, thanks! We'll handle any conflicts that arise with #62