Boarding-pass header with a flight code and music

One file, zero dependencies, “use client” for scroll, the counter, the scroll spy and music. A position:fixed <header> (placement=static puts it in the flow for previews); the [data-part=veil] backdrop with backdrop-filter and a ::after perforation appears on data-scrolled (scrollY>40, first read from rAF) and when the menu is open. The day counter is a per-minute setInterval, empty on the server; it hides via max-height when shrunk. Sections are Oswald caps with a scaleX underline; the active one comes from an IntersectionObserver on the anchors (rootMargin -40 %/-55 %), aria-current. Music is <audio loop preload=none>, play() only on click, aria-pressed, four lines breathe via keyframes. Below 60rem the names and sections move into [data-part=sheet] behind “Menu”. Palette --vibeui-navbar-026-* is neutral: ink and paper via light-dark(), the site colours come through the accent, ink and background props; dark theme via .dark/[data-theme] or tone. Oswald, Lobster and Manrope come via <link precedence> from Google Fonts with system fallbacks. accent and background override colours, prefers-reduced-motion disables animations.