fix: probe Codex auth with the account's default model

The live Codex auth checks in scripts/docker-auth-status.sh and scripts/docker-login.sh probed with -m gpt-5.4-mini, which a ChatGPT-account login rejects ("not supported when using Codex with a ChatGPT account"). A valid login was therefore reported as codex: NOT logged in, and docker-login.sh would force a needless re-login.

This drops the explicit -m flag so the probe uses the account's default model (verified working against a ChatGPT-account login).

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