Link treatment

Global links are intentionally neutral. Only .prose styles them as prose links, and only components style their own link-like elements (nav links, button-as-link, tabs, breadcrumbs, etc.). The reason is that underlining every a globally fights against button-like links, nav links, clickable cards, menu items, and tab triggers. Components that need link semantics should opt in with their own rule. The --link-decoration-thickness, --link-decoration-thickness-hover, and --link-underline-offset tokens have been removed because no global rule consumes them. Prose and components set their own underline metrics inline.