Padrao replicado p/ 2a familia: C++ Abstract (UUIPanel_Base) -> WBP concreto. Arvore: Background(Border) -> Content(NamedSlot) via set_widget_tree; binds casam (Background/Content). Compila 0 erros, parent UUIPanel_Base. Designers injetam conteudo no NamedSlot Content; visual data-driven por FUIStyle.Panel/PanelType. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>