Spark transformer that generates the render/1 function from DSL entities.

Walks the entity tree (screen → container children → leaves) and produces a render/1 that builds the same node maps Dala.Ui.Widgets functions return:

%{type: :column, props: %{...}, children: [...]}

Container entities (column, row, box, scroll, modal, pressable, safe_area) carry a :children field populated by Spark's recursive_as mechanism. Leaf entities have no children.