Codex gate CORE: /api/updates/apply + /force ignored the request-body channel
and re-read the saved setting, so a channel switch whose debounced autosave
hadn't landed could apply the OLD channel. The banner now sends the channel the
CHECK reported for each target; the endpoints validate it against the enum and
thread it into apply_update/apply_force_update (None → saved-setting fallback,
preserving prior behavior). Agent stays channel-neutral server-side.