Module radii
Expand description
Corner radii, by what the corner belongs to (docs/design-language.md,
“Shape”).
Radii are concentric: an inner radius is its container’s radius
minus the inset between them, never below Radii::MIN. A thing that
sits inside another rounded thing asks Radii::concentric for its
radius instead of picking a token, so its corners run parallel to its
container’s at every inset and every scale.