Strange rate limit message

### Describe the bug

Today I started copilot-cli and gave it a quite moderate task.

It starts an background agent and about half a minute later failed with:

> Sorry, you've hit a rate limit that restricts the number of Copilot model requests you can make within a specific time period. Please try again in 2 hours. Please review our Terms of Service (https://docs.github.com/site-policy/github-terms/github-terms-of-service).
> (Request ID: AF08:1CC094:79C2BF:8F5AB7:69C609B2)

Apart from I find the error questionable (it unlikely has done many requests) I think copilot should get some means of reading the limits and take care it does not hit the error (e.g. it can gracefully stop working, throttling, ...) to give a better feedback to the user.

The link itself is rather useless on its own, as it has no indication about copilot limits at all, looking at the copilot settings and the usage shows nothing that explains the error or giving an indication what can be done from a users point of view to avoid the problem. All things are well withing the monthly limit.

### Affected version

_No response_

### Steps to reproduce the behavior

_No response_

### Expected behavior

_No response_

### Additional context

_No response_

バックグラウンドエージェントを起動する中程度のタスクで copilot-cli を開始してレポートを再現し、その後、rate-limit response と request ID を取得します。表示されたガイダンスを Copilot の使用状況/設定およびリンクされた Terms of Service と比較します。limit condition と実行可能な recovery path が明確に伝えられれば完了です。

索引モデルが issue の本文から書いたものです。