Drops out of autopilot after each request

### Describe the bug

It used to be that I would go into autopilot at the beginning (by pressing Shift + Tab twice). Then I would give it a prompt and it would stay in autopilot. I knew this because of the color, the autopilot color was Green (now it's Purple) The color change is fine, but the issue is after a prompt of it being Purple then after the prompt is done it goes back to being Grey. I hit shift tab twice again to put it back into Purple, and then when the prompt is done it goes back to Grey again. Its unclear if its still in autopilot mode. Is it ? Why does it keep going back to Grey after each prompt ? Makes it very hard to tell if i'm still in Autopilot mode. Not sure if this was a bug or a design choice but it makes it very confusing what mode im in.

Thanks

### Affected version

_No response_

### Steps to reproduce the behavior

_No response_

### Expected behavior

_No response_

### Additional context

_No response_

まず Copilot CLI でこれを再現します。Shift+Tab を 2 回押して autopilot に入り、プロンプトを送信し、その後にモードと色が変わるかどうかを確認します。対象となるファイル、テスト、バージョンは指定されていません。各リクエストの後、autopilot の状態が明確で、表示されたインジケーターと一貫していれば完了です。

索引モデルが issue の本文から書いたものです。