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).
A RELAX NG schema document is validated before pattern interpretation
in three layers: the section-3 grammar check (vocabulary, attributes,
arity, text, QNames, datatypeLibrary URIs, hrefs, 4.16 excepts, xmlns
prohibitions), compiler checks (4.17 combine rules, unresolved refs,
parentRef scope, startless grammars, include/externalRef cycles and
overrides, grammar-checked loaded documents, unknown datatypes,
built-in-library params), and the 4.19/7.1-7.4 restrictions over the
compiled algebra after 4.20/4.21 normalization (prohibited paths,
content types, duplicate attributes via representative-name overlap,
infinite-class attributes outside oneOrMore, interleave constraints),
with recursion detection deliberately before normalization. Incorrect
schemas: 213 compiling down to 7, all the pre-Fifth-Edition name-class
class (count asserted). Two leniency tests updated to spec behavior.
Closes#131
