JSON Canonicalization Scheme helpers.
Object member ordering and finite floating-point formatting follow RFC
8785. The raw-text API rejects duplicate object member names and malformed
JSON. Integer tokens that serde_json retains exactly as i64 or u64
are additionally rejected outside [-(2^53)+1, (2^53)-1]; numbers parsed
through binary64, including decimal/exponent forms and magnitudes above
u64::MAX, follow RFC 8785's ECMAScript rounding semantics.