The horizontal scrollbar on the bucket row was ugly and
inconsistent with the rest of the app's scrollbar-less panels. Hide
it, redirect vertical wheel over the bar to horizontal scroll, and
surface overflow with soft bg-coloured gradients on whichever side
has more content off-screen: right only while anchored at the
start, both in the middle, left only at the end.
Fade overlays live on #bucket-row (parent) as pseudo-elements with
pointer-events:none, rather than mask-image on the bar itself — a
mask would also clip super-bucket popovers that are intentionally
rendered inside #bucket-bar for the collab MutationObserver.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>