Expose current-month credit usage via Codex App Server at enterprise plan

What variant of Codex are you using?

App, CLI

What feature would you like to see?

The Codex desktop app Settings > Usage screen shows the current month's credit consumption at enterprise plan. However, Codex App Server does not expose the corresponding value to external local clients.

<img width="1400" height="394" alt="Image" src="https://github.com/user-attachments/assets/d459dc4d-0ffc-4879-a776-9df11b6e161c" />

account/rateLimits/read exposes rate-limit usage and may expose individualLimit (the effective monthly credit limit), but it does not expose the current month's consumed credits or remaining credit balance.

Additional information

I would like to build a small macOS menu-bar app that shows the same current month credit usage visible in Codex Desktop. It should use Codex App Server and supported APIs only, without reading local credentials or calling private backend endpoints. This is the usecase.