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 the WHATWG big5 decoder over the vendored index-big5 (18,590 entries),
for both the whole-buffer and streaming decoders. A lead in 0x81-0xFE plus
a trail in 0x40-0x7E or 0xA1-0xFE resolves through the index, covering
Traditional Chinese and the HKSCS extensions including the astral CJK
ideographs. Four pointers decode to a base letter plus a combining mark.
Selected by the big5 / big5-hkscs declaration names.
Closes#103
