Fix blurring from nav title box shadow (#5374)
Fixes blur noted in https://github.com/astral-sh/uv/pull/5316 but
doesn't drop the title entirely.
https://github.com/astral-sh/uv/pull/5316 is my preferred design, if the
implementation was cost-free.
<img width="1259" alt="Screenshot 2024-07-23 at 3 53 48 PM"
src="https://github.com/user-attachments/assets/6f9b828b-884f-447d-8508-ba4023152e2f">
(nothing to see at the rest of the breakpoints >1220)
<img width="1259" alt="Screenshot 2024-07-23 at 3 53 56 PM"
src="https://github.com/user-attachments/assets/b892cd76-cd91-4e78-b8c8-58e16a8b1130">