fix: make kind non-enumerable

[MisterCommand]

TypeBox v1 has a setting enumerableKind (default false) that makes ~kind non-enumerable on all standard types via Memory.Create(). However, the custom UnionOneOf function sets "~kind" directly on the object literal, making it enumerable — so Ajv sees it and rejects it in strict mode.

The fix is to make ~kind non-enumerable in UnionOneOf, matching how TypeBox v1 handles it internally.

The fix makes ~kind a non-enumerable property on the UnionOneOf schema object, matching how TypeBox v1 handles ~kind internally via Memory.Create(). Previously it was set as a regular enumerable property via object spread ({ ...options, "~kind": "UnionOneOf", oneOf }), which meant Ajv would see it during schema compilation and reject it in strict mode.

[Copilot]

Pull request overview

Adjusts the custom UnionOneOf TypeBox schema helper so its internal ~kind marker matches TypeBox v1’s non-enumerable behavior, avoiding Ajv strict-mode schema rejection.

Changes:

• Make ~kind non-enumerable on the UnionOneOf schema object via Object.defineProperty.
• Minor modification to the file’s header attribution line.

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