Minimal JSON formatting test: keep the escape that matters

To reproduce a JSON Formatter issue, reduce the input to a harmless object that retains the troublesome feature: escaped Unicode, a newline, nested array, large number, or duplicate key. Show exact input and output. Confirm whether both parse and whether values and types match. Do not remove the edge case while simplifying. A minimal sample can reveal whether the formatter only changes whitespace or silently changes data through parser behavior.