.header-shell{position:sticky;top:0;z-index:30;transition:transform .24s ease,background .2s,box-shadow .2s;background:transparent}
.header-shell.header-elevated{background:color-mix(in srgb,var(--paper) 96%,transparent);backdrop-filter:blur(16px);box-shadow:0 1px 0 var(--line),0 8px 24px #0813260a}
.header-shell.header-hidden{transform:translateY(calc(-100% - 2px));pointer-events:none}
.header-shell:focus-within{pointer-events:auto}
@media(prefers-reduced-motion:reduce){.header-shell{transition:none}}
@media(prefers-reduced-transparency:reduce),(prefers-contrast:more){.header-shell.header-elevated{background:var(--paper);backdrop-filter:none}}
@media print{.header-shell{display:none}}