Before-and-after JSON formatting: separate layout from data

Compare the parsed structures before and after JSON formatting. Indentation and object-key order may change without changing meaning, but array order, number-versus-string types, escaped characters, and nulls must be reviewed. A text diff alone can be noisy; a semantic comparison makes real data changes visible. If exact bytes matter to a signature, even layout changes are significant. State which notion of equality is required for this file.