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).
The namespaced derivation backbone keyed every element by the container target
namespace, but a local element is in the target namespace only when qualified (its
own form, else the schema's elementFormDefault). An unqualified local element's
block was keyed {targetNS}name while the instance element is {}name, so
blockedSubstitutionError's lookup missed and a blocked xsi:type substitution on it
was accepted (typeDef00801: a local Element with block="extension" did not bar an
extension substitution).
gatherElement now keys a local element by localElementNamespace (target namespace
when qualified, none otherwise); global elements stay keyed by the target
namespace, and the bare-keyed tables are unchanged.
invalid-instances-accepted 32 to 31, no false positive (valid-instances-rejected
and valid-schemas-rejected held at 0). An adversarial review confirmed qualified
local elements are unchanged, global and same-named local element keys stay
distinct, and a non-blocked substitution on a local element is still accepted.
