message: move z-indices above comments on rarely-used colors
diff: --boxel-success-100: var(--boxel-green);
  --boxel-success-200: var(--boxel-teal);
  - /* Fix: Other colors used in app, potentially not in color palette: */
  -
  /* z-index layers */
  --boxel-layer-modal-default: 15;
  --boxel-layer-modal-urgent: 20;
  - /*
  + /* Fix: Other colors used in app, potentially not in color palette:
  #A5A5A5
  #C1C1D0
  #C9C7DD
  