Shelf clicks in 3D weren't selecting: getSelectionTarget routed shelf
(category='furnish') to the furnish phase, but furnish.isValid hard-
coded `node.type !== 'item'` and rejected shelf. Click switched phase,
nothing selected.
Fix: extend furnish.isValid to also accept registry-driven kinds whose
def.category === 'furnish' AND def.capabilities.selectable. Item's
asset.category door/window special-case stays first.
Future furnish-category kinds (tables, lamps, etc.) are selectable in
furnish phase without further changes.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
