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).
An element ref carrying nillable/default/fixed/form/block, or an element or
attribute ref carrying an inline type definition, was accepted. A ref is a use
of a global declaration, not a declaration, so beyond ref it admits only
minOccurs, maxOccurs, and id (src-element.2.2). The applicability check already
excluded name and type from a ref; this extends the exclusion to the remaining
declaration-only properties and to an inline simpleType/complexType child.
minOccurs/maxOccurs, a group/attributeGroup ref, and an attribute ref's
use/default/fixed (which override on the use) are unaffected.
XSTS: invalid schemas accepted 439 to 424, no other bucket raised. Disclosed
under-detection: a key/unique/keyref child under a ref is not yet flagged.
