OptionalincludeSTEP (AP214/AP242) only: surface ephemeral solid-level nodes beneath
multibody products — pickable bodies that carry identity in the file but
no product semantics (type: 'solid', ephemeral: true). Ignored by the
IFC surface. See design/new/step-nonproduct-semantics.md.
Optional spatial-structure shaping, beyond web-ifc parity.