[FEATURE]: OAuth Device Code flow for ChatGPT / Codex plans

[peixotorms]

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

I noticed that #3281 is now native, and it used oAuth flow, which is great... but this doesn't work on remote servers. We need the OAuth Device Code flow, not the regular oAuth flow.

Please refer to:
openai/codex#9253

On remote servers, it gives a code and we can copy past it for it to connect, much better.

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• /connect doesnt work for openai when server is remote #8274: /connect doesn't work for openai when server is remote - addresses the exact issue of OAuth not working on remote servers
• Enable User Sign-in with Codex ChatGPT Accounts via OAuth #3281: Enable User Sign-in with Codex ChatGPT Accounts via OAuth - the native OAuth implementation mentioned in this issue that doesn't support Device Code flow

The Device Code flow would be particularly useful for remote server scenarios where traditional OAuth (which requires a local callback server) doesn't work. Feel free to ignore if your specific use case differs from these.