BoxNode
data class BoxNode(val children: List<BoxChild>, val width: Dp? = null, val height: Dp? = null, val decoration: ContainerDecoration = ContainerDecoration.None) : PdfNode
Z-stacking container. Children are drawn in source order — first added appears at the bottom, last on top. Each child is positioned at one of the nine BoxAlignment anchor points within the box's interior.
Boxes can be sized explicitly via width / height or wrap their largest child when those are null. They support the same decoration vocabulary as columns and rows (background, border, corner radius, padding).