Add gpt-5 models to the list

[daxian-dbw]

PR Summary

Add gpt-5 models to the list. The gpt-5, gpt-5-mini, and gpt-5-nano will be supported with this change.

[daxian-dbw]

I cannot access GPT-5 but was able to use gpt-5-nano. It doesn't work correctly -- first, it's not fast; second, I only get response for the first query, and nothing for all subsequent queries. Need to look deeper into it, so will close this PR.

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[UPDATE] When using the OpenAI gpt-5 or gpt-5-mini endpoints, I receive explicit errors about "no permission to access endpoint for streaming". Although the gpt-5-nano endpoint doesn't throw the error, I think it's not working due to the same reason.
I will add gpt-5 to the list of supported models for now. Once I have access to gpt-5 model, I can better test it.

[jakupmichaelsen]

I GPT-5 supported now?

After adding GPT-5 in openai.agent.json I simply get:

ERROR: 'gpt-5' is not a supported OpenAI chat completion model.

[daxian-dbw]

@jakupmichaelsen sorry, you will need to use a new build of AIShell to use gpt-5 models. We will think about loosening the check on models.