Default slot — light DOM projected into the shadow tree

Expected: "before <light> after" in each box, i.e. the light-DOM children appear at the slot's position, wrapped by the shadow tree's own text.

Expected: all three light children land in the single default slot, in source order: "before [A B C] after".

Two default slots

Expected: only the first default slot in tree order receives the light DOM. The second renders its fallback text "(empty)".