.layout-shell { grid-template-rows: auto 1fr; }

.header-stack {
  border-bottom: 1px solid var(--border);
  background: var(--panel);
}

.header-stack .app-header { border-bottom: 1px solid var(--border); }

.group-row,
.mode-row {
  display: flex;
  gap: 6px;
  padding: 8px 16px;
  overflow-x: auto;
}

.group-row { border-bottom: 1px solid var(--border); background: #fafcff; }

.group-tab {
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--panel);
  padding: 6px 12px;
  font-size: 12px;
  cursor: pointer;
}

.group-tab.active {
  background: #dbeafe;
  border-color: #93c5fd;
  color: #1e3a8a;
  font-weight: 600;
}

.layout-two-row {
  display: grid;
  grid-template-columns: 280px 1fr 260px;
}

.editor-mock { flex: 1; min-height: 340px; }