Kinds for FSL boundary hooks (on enter/exit &group do 'X' and the plain-
state analogue). These fire post-commit when a transition crosses the
subject's boundary and are not part of HookDescription (that union
covers only the programmatically-registered observational hooks), so the
registry widens its kind field with them.
Kinds for FSL boundary hooks (
on enter/exit &group do 'X'and the plain- state analogue). These fire post-commit when a transition crosses the subject's boundary and are not part of HookDescription (that union covers only the programmatically-registered observational hooks), so the registry widens itskindfield with them.