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.

Start at the --max-ai-credits option handling and trace where low-credit warnings are added to the model context. The issue does not name a file or test, so first identify the warning-injection path and any related CLI tests; done means users can suppress these warnings while the existing credit limit and resume behavior still work.

Written by the indexing model from the issue text.