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).
Limits(strictInternalSubset: true) rejects conditional sections and
parameter-entity references inside markup declarations in the internal
subset, the two feature classes XML 1.0 reserves for the external
subset. DeclSep references and quoted attribute defaults (AttValue)
stay legal; defaults unchanged. The xmltest runner opts in, leaving
case 141 (pre-Fifth-Edition name classes) as its only deviation.
Closes#128
