/* 仅增强现有桌面导航；五项文字与全站字体阶梯一致。 */
.site-header [data-section-nav] { position: relative; }
.site-header [data-section-nav] a { padding-block: 12px; white-space: nowrap; }
.site-header [data-section-nav] a[aria-current="location"] { color: var(--ink); }
.site-header [data-section-nav] a:focus-visible { outline: 2px solid var(--ink); outline-offset: 4px; border-radius: 3px; }

/* 共享一条实底黑条，通过位置与宽度插值在栏目下方移动。 */
.site-header [data-section-nav]::after {
  position: absolute;
  bottom: 4px;
  left: 0;
  width: var(--nav-indicator-width, 0px);
  height: 3px;
  border-radius: 2px;
  background: #0b0d10;
  content: "";
  pointer-events: none;
  opacity: 0;
  transform: translateX(var(--nav-indicator-x, 0px));
  transition: transform .3s cubic-bezier(.22, .68, .3, 1), width .3s ease, opacity .15s ease;
}
.site-header [data-section-nav].has-active-section::after { opacity: 1; }

/* 保密导航定位外层深色画布 #proof；旧 #security 链接仍保留。
   各板块顶部距离固定导航底部约 24px。 */
#business, #expertise, #scope, #practice, #proof, #security { scroll-margin-top: 118px; }
@media (prefers-reduced-motion: reduce) {
  .site-header [data-section-nav]::after { transition: none; }
}