Raised when a 3D areal or linear geometry (%Geo.PolygonZ{},
%Geo.LineStringZ{}, …) is written. #270 Phase 1 supports 3D points
(%Geo.PointZ{}) only; 3D areal/linear geometries are deferred to Phase 2,
because exact 3D containment/distance needs a model the 2D topo refinement
cannot provide. Storing 2D bbox companions would silently drop the z.