Site footer layout shell. Variants: Default (single tier — one permissive footer-main placeholder region), TwoTier (main tier plus a much narrower footer-bottom row, with ShowTierDivider hairline and TierTwoBackground color-scheme options), and Bands (N full-width bands in footer-bands, each child owning its own height, width and surface — with ShowBandDividers ruling every band off from the next). Pick Bands when the footer needs more than two rhythms (slim tagline strip, social/app-badge row, tall link-column block, legal line): Default and TwoTier wrap their region in the container plus a fixed gap, so their children stack at one uniform rhythm and none can paint edge-to-edge, whereas Bands contributes no width, padding or gap and leaves all three to each band (compose section-wrapper per band). The shell owns layout only — surface (ColorScheme/BackgroundIntensity), PaddingY, MaxWidth; compose content into the regions via the stock footer experiences (footer-link-columns, footer-brand-social, footer-legal-strip) or the layout splitters.

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