/* White inset surfaces — charts, tables, snapshot list */
    .ds-chart-card {
      background: var(--ds-surface);
      border: 1px solid var(--ds-border);
      border-radius: var(--ds-radius-md);
      padding: var(--ds-space-4);
    }
    .ds-chart-card--stack {
      display: flex;
      flex-direction: column;
      gap: 0;
      padding: 0;
      overflow: visible;
      border-radius: var(--ds-radius-md);
    }
    details.ds-chart-stack > summary {
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: var(--ds-space-3);
      padding: var(--ds-space-4);
      font-size: var(--ds-text-heading);
      font-weight: 600;
      letter-spacing: 0.01em;
      color: var(--ds-text-secondary);
      list-style: none;
      transition: color 0.15s ease;
    }
    details.ds-chart-stack > summary::-webkit-details-marker { display: none; }
    details.ds-chart-stack > summary:hover { color: var(--ds-text); }
    details.ds-chart-stack[open] > summary .ds-chevron { transform: rotate(90deg); }
    .ds-chart-stack-body {
      display: flex;
      flex-direction: column;
      gap: 0;
      padding: 0 var(--ds-space-4) var(--ds-space-4);
    }
    .ds-chart-card--stack > .ds-chart-stack-body {
      padding-top: var(--ds-space-4);
    }