Match shell squircle outlines with compositor masks

Use shared corner geometry for shell controls, window clipping, materials and blur masks. Preserve circular pills and controls where appropriate, track contour changes in damage, and use tagged ferese-shape and libcosmic dependencies.

compositor/src/presentation.rs

@@ -146,12 +146,7 @@ pub(crate) fn physical_rect(
     )
 }
 
-#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
-pub(crate) enum CornerShape {
-    #[default]
-    Circular,
-    Continuous,
-}
+pub(crate) use ferese_shape::Shape as CornerShape;
 
 /// Conservative extent of the corner shoulders, in physical pixels.
 pub(crate) fn corner_extent(radius: f32, size: smithay::utils::Size<i32, Physical>, shape: CornerShape) -> f32 {