/* ───────── レイアウト基本（左=250px） ───────── */
  body{
    margin:0;height:100vh;
    display:grid;
    grid-template-columns:250px 1fr 250px;
    grid-template-rows:1fr;
    transition:grid-template-columns .3s;
    position:relative;
  }
  .sidebar-left{display:grid;grid-template-rows:180px 1fr;background:#ddd;overflow:hidden}
  .center{display:grid;grid-template-rows:50px 1fr;background:#f9f9f9;overflow:hidden}
  .sidebar-right{
    min-height: 0;       /* ★ gridの子がスクロールできる前提 */
    overflow: hidden;    /* ここは既存のままでOK */
  }
  .frame{border:1px solid #999;box-sizing:border-box}

  body.left-collapsed{grid-template-columns:0 1fr 230px}
  body.right-collapsed{grid-template-columns:250px 1fr 0}
  body.left-collapsed.right-collapsed{grid-template-columns:0 1fr 0}

  .toggle-btn{position:absolute;bottom:10px;width:25px;height:25px;display:flex;align-items:center;justify-content:center;background:#444;color:#fff;border:none;cursor:pointer;opacity:.7;transition:opacity .2s;z-index:1000;font-size:14px;border-radius:5px}
  .toggle-btn:hover{opacity:1}
  .toggle-left{left:250px}
  body.left-collapsed .toggle-left{left:0}
  .toggle-right{right:250px}
  body.right-collapsed .toggle-right{right:0}