Slack-style overlay scrollbar. Hides the native scrollbar so the scrolled content uses the full container width (no gutter reservation), then draws a thin auto-fading thumb absolutely positioned on top. Drag-to-scroll via Pointer Events covers mouse, touch, and pen. Vertical only. The component does not enforce a height — give it a bounded height via the parent (`flex-1 min-h-0` in a flex column, or a fixed `h-*` / `max-h-*`).
npx shadcn@latest add https://uipkge.dev/r/react/overlay-scroll.jsonoverlay-scroll