Allow disabling warning the model when AI credits are low

### Describe the feature or problem you'd like to solve

I set `-max-ai-credits=30` and the model kept getting worried about using all the credits

### Proposed solution

Add an option to suppress whatever warnings are being injected to tell the model it is low on AI credits (or just remove it?).

### Example prompts or workflows

_No response_

### Additional context

I was testing with a local model, and passed `--max-ai-credits=30` (because 30 is the minimum value allowed). The model kept saying "The user is warning me there are only 30 AI credits left so I must be very efficient with my responses".

I can't tell exactly what text was being injected for the model (because when I exported the session there was no such text in there - presumably the export is not complete), but it was happening on every turn. For a local model the credits are not relevant, but even with a cloud model I think I would rather this information be hidden so it won't potentially taint how the model is working. If it runs out, I can `--resume` with another value.

--max-ai-credits オプションの処理から開始し、クレジット残量が少ない場合の警告がモデルコンテキストに追加される箇所まで追跡してください。この issue ではファイルもテストも指定されていないため、まず警告の注入経路と関連する CLI テストを特定してください。既存のクレジット制限と再開動作を維持したまま、ユーザーがこれらの警告を抑制できれば完了です。

索引モデルが issue の本文から書いたものです。