Add xs:any and xs:anyAttribute wildcards with namespace and
processContents constraints (skip/lax/strict), and resolve the
list built-in datatypes (IDREFS, ENTITIES, NMTOKENS) to their
item types so each list item validates.
WildcardNamespace models ##any/##other/enumerated URI sets;
Wildcard.admits gates undeclared attributes and wildcard-matched
children. ContentNFA.follow exposes the follow set for completions.
Closes#77
Compose schemas across documents and resolve types at the instance:
- xs:include, xs:import, and xs:redefine pull a transitive closure of schema
documents through an injected loader (resolved by schemaLocation), base
schemas first so the including schema wins; a redefine's nested definitions
override the schema it includes.
- substitution groups: an xs:element ref to a head also admits every element
that substitutes for it, expanded at parse time into a choice over the head
and its transitive members.
- xsi:type overrides an element's declared type with the named type at the
instance; XML Schema instance attributes are exempt from attribute checks.
The schema parser splits across XSDContext (shared tree helpers, document
collection, parsing context), XSDSimpleParser (simple types and facets), and
XSDParser (elements, complex types, model groups) to keep each within bounds.
Closes#66
