Deterministic CBOR encoder/decoder.

Implements the subset of RFC 8949 needed by Macula records: unsigned ints, byte strings, text strings, arrays, maps, and null.

Encoding follows RFC 8949 §4.2.1 (deterministic):

• Smallest length encoding.
• Definite lengths only (no indefinite items).
• Map keys sorted by bytewise lexicographic order of their deterministic encoding.

Internal value representation:

• non_neg_integer() — uint (major 0)
• binary() — byte string (major 2)
• {text, binary()} — UTF-8 text string (major 3)
• [value()] — array (major 4)
• #{value() => value()} — map (major 5)
• null — simple null (major 7, value 22)