.header-actions { display: flex; align-items: center; justify-content: flex-end; gap: 20px; }
.theme-toggle {
  display: grid;
  place-items: center;
  width: 44px;
  height: 44px;
  flex: none;
  padding: 0;
  border: 1px solid rgba(255,255,255,.15);
  border-radius: 50%;
  color: #e8f1e9;
  background: rgba(255,255,255,.08);
  box-shadow: inset 0 1px 0 rgba(255,255,255,.12), 0 5px 16px rgba(0,0,0,.08);
  -webkit-backdrop-filter: blur(16px);
  backdrop-filter: blur(16px);
  transition: transform .2s ease, background .2s ease, border-color .2s ease;
}
.theme-toggle:hover { transform: translateY(-2px); background: rgba(255,255,255,.15); }
.theme-toggle:active { transform: scale(.94); }
.theme-toggle svg { display: block; width: 20px; height: 20px; }
html[data-theme="light"] .theme-toggle {
  color: #243529;
  border-color: rgba(39,77,46,.15);
  background: rgba(255,255,255,.7);
  box-shadow: inset 0 1px 0 #fff, 0 6px 18px rgba(38,68,44,.08);
}
html[data-theme="light"] .theme-toggle:hover { background: #fff; border-color: rgba(27,103,49,.28); }
html[data-theme="light"] .theme-icon-sun,
html[data-theme="dark"] .theme-icon-moon { display: none; }
@media (prefers-reduced-motion: reduce) {
  .theme-toggle { transition: none; }
}