Add explicit orthogonal span sizing

tests/shrink.rs

@@ -116,6 +116,10 @@ impl Node {
                     children,
                     dir: dir(*down),
                     gap: *gap,
+                    ortho: match down {
+                        true => OrthoSize::Children,
+                        false => OrthoSize::Full,
+                    },
                 }
                 .add(&mut h.rsc);
                 spans.push(handle);