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 relative system identifier declared inside an external entity
resolves against that entity's own URI (RFC 3986, the C14N resolver):
ExternalID gains base and resolvedSystemID, the scanner threads the
current entity's URI through external-subset and PE scans, and
resolvers receive the merged identifier. Clears eduni E18; the eduni
baseline now holds only the grapheme-lexing class (#135).
Closes#138
