Scrollbar Styling and Container Size Utilities in Tailwind CSS v4.3.0

Tailwind CSS v4.3.0 introduces first-class scrollbar styling utilities (width, color, gutter), a new @container-size utility for reading container dimensions inside container queries, zoom-* and tab-* utilities for CSS zoom and tab-size properties, and an expanded @variant directive that accepts stacked and compound variants. The release also adds --default(…) support inside functional utility definitions and fixes to the upgrade tool's canonicalizer for better migration of existing projects.