A generic layout container (pp_box/1), in the spirit of MUI's Box — a bare <div> (or <span>/<pre> via tag=) that exists purely to hold a class, not to apply any visual style of its own.

Unlike every other PhoenixPaper component, pp_box/1 has no paperize attribute — there's no "paper" skin to strip, since it never applies one in the first place. It's a layout primitive, not a styled component; see AGENTS.md, "Component conventions".