ResolveOptionType

type ResolveOptionType = InferChoice<T> extends never
  ? InferCoerce<T, BaseType<T>>
  : T extends { type: "array" }
  ? InferChoice<T>[]
  : InferChoice<T>;

Resolve a single option config to its final type.
Priority: choices > coerce > base type

For array options, choices narrow the element type rather than replacing
the entire type. e.g. { type: 'array', items: 'string', choices: ['a', 'b'] as const }
resolves to ('a' | 'b')[], not 'a' | 'b'.