Update ruby bindings

[alubbe]

I asked Claude Sonnet 4.5 to update the bindings. I don't use these bindings myself, so I can't guarantee that this works, but maybe it's still helpful. Happy to make any changes you'd like.

[alubbe]

I also added more tests and fixed some ruby3.4 warnings (frozen strings and unused variable).
rake test is green

[KitaitiMakoto]

Thank you for the pull request. But, I couldn't evaluate this should be merged or not because I don't know well about copyright and license matters related to LLM.

I really appreciate you noted on Claude.

[alubbe]

My (somewhat limited) legal understanding is that Github Copilot (which I used via VSCode) offers only suggestions, and it is still my code, that I am here volunteering to this Open Source project. https://docs.github.com/en/site-policy/github-terms/github-terms-for-additional-products-and-features#github-copilot

I have also modified most of its suggestions, I just wanted to be transparent about my usage - but I do think that using it is normal now, no?