Fix blurring from nav title box shadow

[zanieb]

Fixes blur noted in #5316 but doesn't drop the title entirely. #5316 is my preferred design, if the implementation was cost-free.

(nothing to see at the rest of the breakpoints >1220)

[charliermarsh]

I think it'd be helpful to include one "Before" pic so we can have a "Before" vs. "After". As-is, it's a little hard for me to know what the effect was as the reviewer.

[zanieb]

Sorry still trying to figure out how to present all the breakpoints as well as the key change.

The "before" image is at #5316 (comment)

Here's the "after":