prevent case sensitivity api response errors

[tillydray]

I was updating to the omni model and used all caps

    (setq org-ai-default-chat-model "GPT-4o")
    (add-to-list 'org-ai-chat-models "GPT-4o")

I got this error response The model GPT-4o does not exist or you do not have access to it. So I changed it to lowercase and it worked.

    (setq org-ai-default-chat-model "gpt-4o")
    (add-to-list 'org-ai-chat-models "gpt-4o")

it's a minor issue but some people might get stuck on this for some time. lower casing the model would help and maybe providing a warning message that models should be lowercased?