Fold, rotation, and Split View all change size class — how do we tell them apart?

We currently dismiss and rebuild a presented sheet whenever horizontalSizeClass changes. That also fires for rotation and for Split View or Stage Manager resizing. Is there a callback or geometry value that means “the device folded or unfolded,” separate from a normal size transition?

Fold, rotation, and Split View all change size class — how do we tell them apart?
 
 
Q