public extension PureYAML.Streaming {
    /// The result of one ``Scanner/next()`` call.
    enum Outcome: Equatable, Sendable {
        /// A token is ready.
        case token(Token)
        /// The buffered input was exhausted mid-scan; call ``Scanner/feed(_:)``
        /// with more input (or ``Scanner/finish()`` if there is no more) and
        /// call ``Scanner/next()`` again.
        case needMoreInput
        /// The stream has ended; no further tokens remain.
        case done
    }
}