Codex's sign-in, ChatGPT, keeps Codex signed in to ChatGPT with magpie's
models beside its own, but once the ChatGPT account is used up magpie
makes itself Codex's provider (#540): the Codex app sends nothing at all
on an account it knows is out, a magpie model's turn included. That move
went unsaid, and a user who chose ChatGPT expected Codex to stay there.
ChatGPT now says it, and a third way, Always ChatGPT (login "chatgpt"),
never makes the move, by a pick or by Sync; choosing it puts a Codex moved
before back beside the sign-in. What it costs is said beside it: the Codex
app may send nothing till the account has room, while Codex CLI's turns
still reach magpie by the base URL, its routing and other accounts serving
them.