serp-random

Drop-in replacement for CPython's random module (docs/libraries.md drop-in facade push).

• from serp_random import seed, random, randint, uniform, randrange, getrandbits, choice, shuffle
• The generator is MT19937 (Mersenne Twister), implemented bit-for-bit like CPython: the same seeding (init_by_array over the integer's 32-bit limbs), genrand_res53 floats, and _randbelow rejection sampling. A seeded sequence is identical to CPython's random module — and therefore byte-identical across native builds and CPython runs.
• seed() with no argument seeds from OS entropy; seed(n) is reproducible.
• Architecture: serp_random is a pure-Serpentine facade over the compiler-known serp_random_core rtlib module (MT19937 lives in the native runtime; the CPython delegate drives the stdlib's global Mersenne Twister).
• Divergences: getrandbits(k) caps at 63 bits (native int64); randrange/randint widths must fit in int64; error messages pinned to CPython 3.11; sample, choices, the distribution functions, and the Random class are not provided.
• choice/shuffle work with lists of Copy elements (int/float/str/bool/bytes).

Install into a Serpentine project with serp add serp-random.