Theme

src/theme/index.ts — ThemeName (light-neutral, light-warm, dark-slate, dark-contrast), ThemeTokens (--pde-*), themes, themeCss(name), allThemesCss().

All colors/dimensions via CSS variables, no literals outside themes/. themes/base.css + themes/components.css (includes equationCss, iconCss).

See docs/guide/themes.md.