/* ── 双层导航：topnav + subnav ── */
.topnav { border-bottom: none; }

.subnav {
  border-bottom: 1px solid var(--border);
  background: var(--bg);
}
.subnav-inner {
  display: flex; align-items: center; justify-content: space-between;
  height: 40px; padding: 0 var(--container-gutter);
  max-width: var(--container-max); margin-inline: auto;
}
.subnav-inner a {
  font-size: var(--fs-sm); color: var(--muted);
  padding: 4px 0; text-decoration: none;
  white-space: nowrap;
}
.subnav-inner a:hover { color: var(--fg); }
.subnav-inner a.active {
  color: var(--fg); border-bottom: 2px solid var(--accent);
  padding-bottom: 0; margin-bottom: -1px;
}

@media (max-width: 768px) {
  .topnav-inner { height: 48px; }
}