public extension PureYAML.Validation {
    /// The read-only bundle a type-directed check receives: the whole `document` (for cross-cutting
    /// checks), the current `subject` of the check's type, and the `path` to where it sits. `Document`
    /// is the type of the validated tree's root, so each layer carries a truthful document: `Model.Value`
    /// for the model tree, `Tagged.Node` for the tagged tree.
    struct ValidationContext<Subject: Validatable, Document: Sendable>: Sendable {
        public var document: Document
        public var subject: Subject
        public var path: Path

        public init(
            document: Document,
            subject: Subject,
            path: Path,
        ) {
            self.document = document
            self.subject = subject
            self.path = path
        }
    }
}