codex OAuth support

[JMKJR]

Has thought been given to supporting OAuth login for codex ACP? Currently only API key is supported. This means GPT premium subscribers can't leverage their paid plan (via OAuth) and would instead incur usage fees if they opted for the API key route.

I experimented with changing the codex provider command to codex mcp-server (with codex already logged in via cli) hoping that Avante would be able to communicate through this stdio transport. However, opening a new Avante ask session causes neovim to crash without error.