This PR is an additive change introducing the `truncate_start` method to
labels, which gives us the ability to add an ellipsis at the beginning
of the text as opposed to the regular `truncate`. This will be generally
used for truncating file paths, where the end is typically more relevant
than the beginning, but given it's a general method, there's the
possibility to be used anywhere else, too.

<img width="500" height="690" alt="Screenshot 2025-12-17 at 12  35@2x"
src="https://github.com/user-attachments/assets/f853f5a3-60b3-4380-a11c-bb47868a4470"
/>

Release Notes:

- N/A

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Co-authored-by: Lukas Wirth <lukas@zed.dev>