Group @testable imports at the bottom, per public/rules-swift's swiftformat. A
behavior-preserving import-ordering reformat across 252 files (mostly tests).
--trailingclosures was deliberately not adopted (cosmetic, and swiftformat flags
it as caution-worthy).
- Eval-time prefix bindings: Query.evaluate(over:namespaces:) and
value(at:...:namespaces:) supply prefix to URI bindings, so a name test
like q:item resolves q to a URI and matches by namespace regardless of
the document's own prefix. The match is namespace-aware only when
bindings are present, so existing unprefixed/prefix-string queries are
unchanged.
- XPointer schemes: xpath1() evaluates an XPath expression (like
xpointer()), and xmlns(p=uri) binds a prefix for the expression parts
that follow it, threaded into the XPath evaluation.
The range() scheme (and so XInclude range inclusion) remains.
Part of #88
