This PR fixes a long repo name pushing the branch selector off the
screen, as well as just generally truncating them down in a way smarter
than a fixed character limit when long.

| Before | After |
|---------|-----------|
| ![CleanShot 2025-03-11 at 17 21
31@2x](https://github.com/user-attachments/assets/8762b5a7-883c-4080-a6cf-e8007c4737e7)
| ![CleanShot 2025-03-11 at 17 21
44@2x](https://github.com/user-attachments/assets/c3904c29-d939-445f-b700-5bf73f257256)
|


Release Notes:

- Git Panel: Smart truncate long branch and repository names in their
respective selectors