Line heights

The framework exposes three line-height tokens:

• --line-height-tight (1.25) — used by global headings and by display / title classes
• --line-height (1.5) — body default
• --line-height-relaxed (1.75) — used by .lead and .text-lead for intro text

There is no --line-height-normal. It would be redundant with --line-height. Prose overrides line-height through --prose-line-height and --prose-heading-line-height because the readable values for long-form text are different from app UI.