[Bug]: When exporting the image, there is a gray border.
### What happened?

When exporting the image, there is a gray border.

<img width="466" alt="Image" src="https://github.com/user-attachments/assets/e55bfbef-f741-4975-b781-5ac195f57021" />

This happens on  https://tldraw.dev. I was unable to reproduce it in https://tldraw.com

### How can we reproduce the bug?

1. Visit https://www.tldraw.dev
2. Create a rectangle shape with some text in it
3. Go to Export -> PNG

### What browsers are you seeing the problem on?

Chrome

### Where did this happen?

The tldraw.dev website

### Contact Details

joyfunc@gmail.com

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct