The two monolithic XSD content/identity rules only satisfied the OpenAPIKit
validation idiom at the wrong granularity: no per-constraint removability,
no isolable failing/near-miss tests. Split them into 32 named rules, each
finding tagged at its origin and cached per XSDContext so the walk still
runs once per document (the #101 decision against duplicating XSD's
recursive type resolution still holds). Wired the streaming path's ID/IDREF
and identity checks through the same framework instead of calling the
validators imperatively, and added the unwrapAndLookup combinator the rule
already named as required.
Also includes the mandated repo-wide swiftformat/swiftlint pass.
Add EUC-TW for the whole-buffer and streaming decoders: ASCII, a two-byte
plane-1 pair, and a 0x8E four-byte plane selector plus a pair. CNS planes 1
and 2, which carry essentially all real-world EUC-TW text, are vendored from
the ICU euc-tw-2014 mapping (private-use fallbacks dropped); planes 3-15 are a
documented follow-up. Tested for plane 1 (two-byte and four-byte forms), plane
2, and streaming. The streaming method moved to its own file to stay under the
type-body cap.
Closes#108
