Configuration contract for a singular typed embedded Ash resource.

Configure the embedded resource's fields recursively with child_fields in AshBackpex.LiveResource. This module defines the configuration boundary used by AshBackpex's singular embedded-resource renderer. It is distinct from Backpex.Fields.InlineCRUD, which represents repeated children.

The parent Ash action accepts a singular embedded value as a map. Repeated typed embeds use InlineCRUD and are normalized to ordered lists of maps.