Follow-up: Blame view - "authored" line leaking into next row

What does this MR do and why?

1. Follow-up on the nitpick about shorter notation for conditional classes: !142043 (comment 1738728189)
2. Fine tuning the spacing -   did cause a double space for the elements outside flexbox context. I decided to include a gap property based on ch unit and adjust width limit of the author accordingly.
3. Bonus 🎁 a small fix for a recent regression - !142431 (comment 1740597789)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Change your username to something long
2. Go to Repository page
3. Open a file and click Blame button on a top bar of a file holder (beware that there is a new blame view at the top of the repository view and it doesn't have this bug).
4. Make sure the name is truncated and you can easily read the date of the commit

Related to #435124 (closed)