Path bar active state papercuts

The hover/active state on path bar items currently looks a bit unpolished:

The main issues to my eyes here are:

• The bounding box of the items touching the dividers. I'd try about 3px margins around them.
• The rounded edges touching the edge of the container, which isn't something we do anywhere. We could either keep the size but stop rounding the edges, or maybe make the items less tall so we can have a few pixels of padding around the box.