Support string coercion for array-form type in OpenAPI 3.1 (runtime) - #21

problem

committee passes query, path, and form params to openapi_parser as raw Strings and relies on coerce_value to convert them. 3.1 removed nullable, so a nullable param is written as type: [integer, "null"]. array-form type picks a type by matching the value's class, so "5" matches nothing and fails validation. every request that sends a nullable non-string param is rejected.

solution

• with coerce_value on, a String that matches no type in an array-form type is coerced by trying each listed non-null type in order ("5" against [integer, "null"] becomes 5)
• returns the first type that validates, otherwise the first type's error
• exact class matches are unchanged (a String against [integer, string] stays a String)
• not gated on document version, matching the other 3.1 runtime changes; array-form type is already flagged in 3.0 docs by TypeArrayIn30
• no new SpecValidator rule, since this only changes runtime behavior for an existing keyword

depends on #14.