Orbital theme — CSS variable injection and runtime customization.
Provides [OrbitalThemeProvider] and theme hooks for light/dark mode, brand
color, density, typography, spacing, and elevation overrides.
First-paint baseline
[default_first_paint_baseline_css] and [ROOT_THEME_SCOPE_ID] supply SSR shell
CSS (fonts + scoped light-theme vars). Wire into the document shell via
orbital::OrbitalFirstPaintHeadAssets. Dark mode, custom brand, and route-specific
brand remain runtime responsibilities after hydration.