The sealed class hierarchy graph generates bad link for member classes, which drops the simple name of the outer classes; see the ValueLayout example:
https://download.java.net/java/early_access/jdk21/docs/api/java.base/java/lang/foreign/ValueLayout-sealed-graph.svg

In addition, if a subclass class is not enclosed in its sealed superclass, it's preferable to generate the qualified name (with outer class simple name but no package) as the text on the class node, like B.C extends A, then we shouldn't render A <- C, but should render A <- B.C instead.