Site header chrome — a pure-placeholder shell with no datasource fields. Compose logo/nav/utilities/mobile-menu renderings into its seven slots (announcement, utility start/end, start, nav, end, mobile). Pick the arrangement by VARIANT: Standard (start/nav/end bar), TwoTier (slim utility strip on its own tinted top band with the brand + nav bar below), CenteredStack (brand row centered, nav on a bordered row below), CenteredInline (single-row centered-logo masthead — MenuPlacement picks the menu side), Overlay (floats transparently over the page's first full-bleed hero with light-on-dark text). Sticky pins the bar; ColorScheme/BackgroundIntensity/SurfaceColor tint it.

• src/components/registry/components/layout/header.tsx→components/registry/components/layout/header.tsx
• src/components/registry/components/layout/header.recipe.ts→src/recipes/header.recipe.ts