The Foundry document name (e.g. "Actor").
The document sub-type value (e.g. "cohort").
The already-localized base label for the type.
A localization function (sohl.i18n.localize in production).
The label, suffixed with (Experimental) when the type is fenced.
Append a localized "(Experimental)" suffix to a type's display label when that
(documentName, type)is fenced; otherwise return the label unchanged. Pure so the create-dialog label logic is unit-testable without Foundry — the caller injects the localizer.