Minimal JSON diff test: distinguish null, missing, and type

A tiny JSON Diff example can use two harmless objects where one key is missing, another is null, and a value changes from number to string. Include an array whose order changes if ordering matters to the real case. State which differences you expect the tool to show. Keep both documents valid JSON and free of secrets. This sample reveals whether the comparison is semantic, text-based, or normalizing away a meaningful distinction.