/* ============================================================
   Site header — sticky, blur, logo lockup, nav
   ============================================================ */
.site-header {
  position: fixed;
  inset: 0 0 auto 0;
  z-index: 100;
  border-bottom: 1px solid transparent;
  transition: box-shadow var(--dur) var(--ease),
              border-color var(--dur) var(--ease);
}
/* Frosted background lives on a pseudo-element, NOT the header itself: a
   backdrop-filter on .site-header would make it the containing block for the
   fixed mobile drawer (collapsing the drawer into the header's height). */
.site-header::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: -1;
  background: rgba(255, 255, 255, .85);
  -webkit-backdrop-filter: saturate(140%) blur(12px);
  backdrop-filter: saturate(140%) blur(12px);
  transition: background var(--dur) var(--ease);
}
.site-header.is-scrolled::before { background: rgba(255, 255, 255, .97); }
.site-header.is-scrolled {
  box-shadow: var(--sh-header);
  border-bottom-color: var(--line);
}

.site-header__inner {
  height: var(--header-h);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
  transition: height var(--dur) var(--ease);
}
.site-header.is-scrolled .site-header__inner { height: var(--header-h-scroll); }

/* Brand lockup: official logo + project name */
.brand {
  display: flex;
  align-items: center;
  gap: .85rem;
  flex-shrink: 0;
}
.brand__logo {
  height: 26px;
  width: auto;
  transition: height var(--dur) var(--ease);
}
.site-header.is-scrolled .brand__logo { height: 23px; }
.brand__sep {
  width: 1px;
  height: 30px;
  background: var(--line);
}
.brand__project {
  font-family: var(--font-sans);
  font-weight: var(--fw-med);
  font-size: .95rem;
  letter-spacing: .01em;
  color: var(--brand-700);
  white-space: nowrap;
}

/* Navigation */
.site-nav {
  display: flex;
  align-items: center;
  gap: 1.6rem;
}
.site-nav__list {
  display: flex;
  align-items: center;
  gap: 1.5rem;
}
.site-nav__link {
  position: relative;
  font-size: .9rem;
  font-weight: var(--fw-reg);
  color: var(--body);
  padding: .3rem 0;
  transition: color var(--dur) var(--ease);
}
.site-nav__link::after {
  content: "";
  position: absolute;
  left: 0; right: 100%; bottom: -1px;
  height: 1.5px;
  background: var(--brand-600);
  transition: right var(--dur) var(--ease);
}
.site-nav__link:hover { color: var(--brand-700); }
.site-nav__link:hover::after { right: 0; }

/* Header actions (desktop CTA + mobile toggle) */
.site-header__actions {
  display: flex;
  align-items: center;
  gap: .75rem;
  flex-shrink: 0;
}
.header-cta { flex-shrink: 0; }

.nav-toggle {
  display: none;
  font-size: 1.65rem;
  line-height: 1;
  color: var(--ink);
  padding: .2rem;
}
.site-nav__cta { display: none; }