Fast non-cryptographic PRNG NIF (wyrand).

Drop-in replacement for granderl:uniform/1. Per-OS-thread state via __thread, lazy-seeded from getrandom/arc4random_buf on first use. Biased multiply-and-shift bounded output -- single multiply, no rejection branch (modulo bias under 1e-7 for bounds up to 256, invisible at typical workload scale).

Use knot:uniform/1 to draw a uniformly distributed integer from 1..N. For bounds > 4294967295 (2^32 - 1), the NIF rejects with badarg -- the C-side argument is an unsigned 32-bit int.