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 eduni sections run with exact classified baselines. Fixes: 3.3.3
CDATA attribute-value normalization (literal whitespace to space before
reference decoding; char-ref whitespace survives; tokenized collapse on
SPACE only); production-68 lenient undeclared entities in content and
attribute values (validity finding, reference kept literal, nothing
fetched); errata E15 (references/comments/PIs/whitespace in EMPTY,
char-ref whitespace as data in element content, double-escape shape
included); errata E2 duplicate enumeration tokens; errata E14
declarations completed inside PE replacements (VC: Proper
Declaration/PE Nesting); NCName ID values; namespace declarations
subject to the every-attribute-declared rule. Reader validity machinery
split to EventReaderValidity for caps.
Closes#127
