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 reader buffers one Unicode scalar per element, splitting
multi-scalar graphemes from any source, so combining marks cannot merge
with delimiters and the Fifth Edition's scalar-defined name productions
classify correctly; the replacement-text, content-model, and ATTLIST
sub-scanners and the entity-literal validator follow, while grapheme
clusters reassemble wherever scanned text accumulates. Clears the last
eduni baseline, grows the asserted IBM pre-5e class to 300, and with
the xmltest manifest's own EDITION exclusions for 140/141 empties the
xmltest baseline: every xmlconf case applicable to a Fifth Edition,
namespace-aware processor passes.
Closes#135
