Dropdown nav panel — columns of link lists, a featured slot, and a CTA strip. Drops into a main-nav item's panel placeholder or anywhere a header utility opens a panel.

• src/components/registry/components/layout/mega-menu.tsx→components/registry/components/layout/mega-menu.tsx
• src/components/registry/components/layout/mega-menu.recipe.ts→src/recipes/mega-menu.recipe.ts