fieldPredicate's oneOf branches use `not: {required: [...]}` to make
values/number exclusive; the validator had no "not" handling at all, so it
silently ignored the keyword and FieldPredicate_ValuesAndNumberTogether_FailsItsSchema
found nothing wrong. A schema matches "not" when validating against the
subschema produces zero errors, in which case the instance must not match it.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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