chore: audit all components (#2)

Reviewed-on: #2

crates/core/tests/scroll_area.rs

@@ -88,13 +88,6 @@ fn the_content_starts_unscrolled_and_horizontal_axes_scroll_x() {
     assert_eq!(handle.offset().x, px(0.));
 }
 
-#[test]
-fn the_thumb_paints_when_the_content_overflows() {
-    let (_cx, _visual, handle) = scroll_area_window(30);
-    // 30 rows × 20px in a 200px viewport: the thumb has something to report.
-    assert!(handle.max_offset().y > px(0.));
-}
-
 /// The gallery's exact shell: a window-filling root, a window-filling scroll
 /// area over padded flex-column content that towers past the viewport.
 struct GalleryShell {