The previous binding pulled the bar 44px up from body-row's top
(`body-row.y - self.height`), which landed it inside the artist
header — eating the action buttons row. The right value is
`body-row.y` itself: the bar takes the top 44px of the 52px
reservation slot that lives as body-row's first child, so it sits
exactly in the gap between the header above and the body below
(Popular Tracks header starts 52px into the body row, giving an
8px breathing gap below the bar). No overlap on either side.
Sidebar natural-top compensates with `+ jump-nav.height` so it
still starts flush with the bar's bottom edge as before.
cc
vicrodh
69029238ee