Anchor that pins the diagonally-opposite (fixed) corner. Always the
axis-wise opposite of {xEdge, yEdge}.
Affordance/handle discriminator string for this corner.
Short positional tag ('<xEdge>-<yEdge>'), e.g. 'min-max'.
Which x-edge the corner sits on ('min' = left, 'max' = right).
Which y-edge the corner sits on ('min' = top, 'max' = bottom).
One entry of the canonical 4-corner resize layout. The single source of truth for "which corner maps to which anchor / handle-kind".