GeometryLayout_min = (a, b) => {
      if (a === b) {
        return a;
      }

      if (a === 'XYZM') {
        // anything `b` is minimum
        return b;
      }
      if (b === 'XYZM') {
        // anything `a` is minimum
        return a;
      }

      // otherwise, incompatible
      return 'XY';
    }
@param {import("../geom/Geometry.js").GeometryLayout} a A
@param {import("../geom/Geometry.js").GeometryLayout} b B
@return {import("../geom/Geometry.js").GeometryLayout} minimum layout made by common axes