/* 导航下拉 */
.main-nav .drop { position: relative; }
.main-nav .drop > a::after { content: " ▾"; font-size: 10px; color: var(--faint); }
.main-nav .menu { position: absolute; top: calc(100% + 8px); left: 0; min-width: 220px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--r-md);
  box-shadow: 0 16px 48px rgba(0, 0, 0, .5); padding: 6px; opacity: 0; visibility: hidden; transform: translateY(-6px);
  transition: opacity .15s var(--ease), transform .15s var(--ease), visibility .15s; max-height: 70vh; overflow-y: auto; z-index: 60; }
.main-nav .drop:hover .menu, .main-nav .drop.open .menu { opacity: 1; visibility: visible; transform: none; }
.main-nav .menu a { display: block; padding: 8px 12px; border-radius: 6px; font-size: 13.5px; color: var(--muted); }
.main-nav .menu a:hover { background: var(--surface-hover); color: var(--text); }
.main-nav .menu a.active { color: var(--accent); }