.layout {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 3rem;
  align-items: start;
}

.sidebar {
  position: sticky;
  top: 2rem;
  max-height: calc(100vh - 4rem);
  overflow-y: auto;
}

@media (max-width: 900px) {
  .layout { grid-template-columns: 1fr; }
  .sidebar { position: static; }
}