The namespace layer rejects malformed qualified names, declarations of
the xmlns prefix, misbindings of the xml prefix and either reserved
namespace name (including as the default namespace), and prefix
undeclaration; attributes must be distinct by expanded name; PI targets
and entity/notation names are NCNames; and DTD-typed xmlns values bind
their normalized form. Clears all 18 namespace cases from the eduni
baseline; xmltest valid/sa/012 joins the documented deviations per the
suite's own NAMESPACE='no' flag.
Closes#136
Add namespace resolution following the XML Namespaces rules, reimplemented in
Swift from libxml2's SAX2 model; no upstream code copied.
- QualifiedName gains an optional resolved namespaceURI (nil for names built
directly or in no namespace), with a resolved(namespaceURI:) helper.
- NamespaceContext maintains a scope stack of xmlns bindings as elements open
and close, resolving element and attribute names against it.
- A default namespace applies to unprefixed element names but never to
attributes; the xml prefix is built in; xmlns declarations are preserved as
attributes so documents round-trip; an unbound prefix raises
ParseError.undefinedNamespacePrefix. End-tag matching stays lexical.
- Namespace-free documents are unchanged (URIs remain nil).
- 7 namespace tests; 39 total.
