Remove all remaining WHAT DOM access which isn’t encapsulated by what…

…DOMAdapter*

* I manually validated this by looking for any references in project to the types in DOM.compat-min.ts. One minor **type only** exception is references to types of the `XPathResult.*_TYPE` constants. This does suggest that there’s some small risk that future maintenance may mistakenly reintroduce WHAT DOM access somewhere it isn’t expected and encapsulated. The risk should be very small so long as we retain the opaque nature of `XPathNode` and its subtypes.

packages/xpath/src/adapter/WHAT/WHATNode.ts

@@ -75,26 +75,3 @@ export type WHATNamedNode = UnwrappableWHATNodeUnion<
 	// eslint-disable-next-line @typescript-eslint/sort-type-constituents
 	Element | Attr
 >;
-
-/**
- * @todo This is temporary! It can be removed once existing WHAT Working Group
- * DOM access is fully isolated to the WHAT adapter. In so doing, it also makes
- * sense to invert the interface extension relationship and remove direct
- * {@link XPathNodeKindKey} definitions on each of the `WHAT*` interfaces. (We
- * cannot do that now, because it would create an inheritance cycle.)
- */
-declare module '../interface/XPathNode.ts' {
-	export interface XPathDocument extends WHATDocument {}
-
-	export interface XPathElement extends WHATElement {}
-
-	export interface XPathNamespaceDeclaration extends WHATNamespaceDeclaration {}
-
-	export interface XPathAttribute extends WHATAttribute {}
-
-	export interface XPathText extends WHATText {}
-
-	export interface XPathComment extends WHATComment {}
-
-	export interface XPathProcessingInstruction extends WHATProcessingInstruction {}
-}