nx_uuid.nx

nx_uuid.nx -- RFC 4122 UUIDv4 + RFC 9562 UUIDv7. Used by: - Distributed log correlation (request IDs) - Database row primary keys (when an external system needs them before insert) - Cache key generation UUIDv4 is fully random (122 bits of entropy + 6 fixed bits). UUIDv7 is timestamp-prefixed (48 bits Unix-ms timestamp + 74 bits of entropy + 6 fixed bits) -- sortable by creation time, which makes B-tree primary keys 100x faster on insert than v4. Both are 128-bit values rendered as "xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx" where M = version digit (4 or 7) and N's high 2 bits are 10 (RFC variant marker). We accept any nx_rng for the entropy source. v7 uses gettimeofday() for the timestamp. Pairs with nx_random (entropy) + nx_strconv (hex output).