@media (min-width: 900px){
  .split{
    display:grid;
    grid-template-columns:1fr 1fr; /* Editor | Viewer */
    height:calc(100vh - 58px);
  }
  .pane{border-bottom:none}
  #editorPane{border-right:1px solid var(--border)}
  .tabs{display:none} /* PC không cần nút chuyển */
  body[data-page="editor"] #viewerPane,
  body[data-page="viewer"] #editorPane{display:block !important;}
}