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.

shell/ferese-shell/Cargo.toml

@@ -17,7 +17,7 @@ libc.workspace = true
 # Keep GPU rendering available as a fallback/override. The shell defaults to
 # tiny-skia to avoid a second GPU initialization during desktop startup.
 libcosmic = { workspace = true, features = ["wgpu", "a11y"] }
-iced_accessibility = { git = "https://github.com/pop-os/libcosmic", rev = "03d7dcb832bc6d15bc1bb07327a1aa426b2d5bc0" }
+iced_accessibility = { git = "https://github.com/ferese-wm/libcosmic", tag = "ferese-v0.1.0" }
 serde.workspace = true
 serde_json.workspace = true
 tempfile.workspace = true