Point counterpart of apply_layer_affine_to_rect: scale about the layer
pivot, then translate. Rotation/perspective are deliberately excluded — the
affine space is the one SDF shapes are evaluated in, with rotation carried
by the deformed quad instead.
Extends an ancestor mapping from untransformed layout coordinates to window
coordinates with this node’s graphics layer. origin and bounds describe
the node before any ancestor transforms; bounds is relative to origin.