/* ============================================
   HEADER — Subtractive & Minimalist Top Bar
   ============================================ */

.site-header {
  position: sticky;
  top: 0;
  z-index: var(--z-sticky);
  width: 100%;
  background: rgba(6, 6, 8, 0.7);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid rgba(255, 255, 255, 0.06);
  transition: border-color var(--transition-fast), background-color var(--transition-fast);
  animation: navEntrance 0.5s var(--ease-out) forwards;
}

[data-theme="light"] .site-header {
  background: rgba(246, 247, 249, 0.8);
  border-bottom: 1px solid rgba(10, 15, 30, 0.06);
}

.site-header.is-scrolled {
  border-bottom-color: rgba(255, 255, 255, 0.12);
}

[data-theme="light"] .site-header.is-scrolled {
  border-bottom-color: rgba(10, 15, 30, 0.1);
}

.header-inner {
  max-width: 960px;
  margin: 0 auto;
  height: 56px;
  padding: 0 var(--sp-4);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

/* Brand mark */
.brand-logo {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
}

.brand-avatar {
  width: 28px;
  height: 28px;
  border-radius: 7px;
  overflow: hidden;
  background: var(--bg-surface-elevated);
}

.brand-avatar img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.brand-name {
  color: var(--text-primary);
  font-size: var(--text-sm);
  font-weight: 700;
  letter-spacing: -0.02em;
}

/* Right-aligned quiet navigation */
.header-actions {
  display: inline-flex;
  align-items: center;
  gap: var(--sp-4);
}

.header-link {
  color: var(--text-secondary);
  font-size: var(--text-sm);
  font-weight: 500;
  text-decoration: none;
  transition: color var(--transition-fast);
}

.header-link:hover {
  color: var(--text-primary);
}

.theme-toggle-btn {
  width: 32px;
  height: 32px;
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: color var(--transition-fast), background-color var(--transition-fast);
}

.theme-toggle-btn:hover {
  color: var(--text-primary);
  background: var(--bg-surface-elevated);
}

.theme-toggle-btn svg {
  width: 15px;
  height: 15px;
}

@keyframes navEntrance {
  from {
    opacity: 0;
    transform: translateY(-8px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}