Rewrites JSON-roundtripped Zod 4 schema objects that leak Zod internals as
JSON Schema keywords (e.g., `type:"enum"`, `enum:{...}`) into valid
JSON Schema 2020-12. This prevents validation failures when such schemas
are used as tool input schemas (e.g., from MCP servers).
Updates `isZodSchema` to reject deserialized Zod impostors that retain
`_zod` but lose their prototype.
Wires `toJSON` methods onto TypeBox shim schemas to ensure `JSON.stringify`
produces clean JSON Schema, preventing future leaks.
Fixes#1101
Can Bölük
4024fbe7e2