Facade Zone
The volume immediately against a building's external wall, read as the zone in which the facade build-up, its junctions and its ground condition are specified together.
Names a set of surfaces rather than a volume, and fails the standing-in test the way `home_exterior` does. Retained because the spine carries it and because facade packages really are specified as one zone. If it is ever split, its contents belong in ELEMENT - `element.cladding`, `element.external_wall` - and not here.