[Bug]: Arrow labels can be truncated when exporting
### What happened?

When an arrow label overflows the bounding box created by other items, it ends up being truncated in exports.

### How can we reproduce the bug?

Given the following starting point

![CleanShot 2025-01-15 at 14 12 42](https://github.com/user-attachments/assets/e9d33835-37fd-465b-a88d-e22343dbe24e)

doing a drag-selection over the entire area results in

![CleanShot 2025-01-15 at 14 13 01](https://github.com/user-attachments/assets/d493bb7a-3c77-446c-bbb7-8fc02423c412)

which if you then export (via the top-level export menu or by right-clicking on the selection) you get

PNG | SVG
---- | ----
![truncated](https://github.com/user-attachments/assets/51e70c2d-f62b-480c-bbf2-5a8884835577) | ![truncated](https://github.com/user-attachments/assets/a01ca3dc-5525-4d19-9846-afa3e328f274)

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

Firefox

### Where did this happen?

The tldraw.com website

### Contact Details

_No response_

### Code of Conduct

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