JSON Formatter final check: compare parsed values

Formatting JSON should change readability, not data. After formatting, parse the output and compare keys, values, types, arrays, and nulls with the original. Watch duplicate keys: some parsers silently keep only one value, so formatting can appear to normalize a problematic input. Check escaped Unicode and line breaks if those matter to the consumer. A neatly indented document may still violate a schema or carry an incorrect endpoint; formatting is not validation.