tests/pytest_random_plugin.py: --seed does not seed Python's `random` module

[yurekami]

The autouse seed fixture in tests/pytest_random_plugin.py calls
torch.manual_seed(seed) but does not call random.seed(seed).

tile_kernels/testing/generator.py:94 (generate_rand_float) picks the
magnitude exponent via random.randint(-110, 126). So the input scale
used by tests like tests/quant/test_per_block_cast_lossless.py varies
across runs even when the user passes --seed. That defeats the
plugin's stated purpose.

Reproduction

A torch-free reproduction (the entropy source in question is pure
Python stdlib):

import hashlib, random

def fixture(node_id, base=0):
    h = int(hashlib.sha256(node_id.encode()).hexdigest(), 16) % (2**31)
    return base + h  # plugin currently seeds torch here, not random

node = 'tests/quant/test_per_block_cast_lossless.py::test[num_tokens=4001-hidden=2048]'
fixture(node, base=0)
run1 = [random.randint(-110, 126) for _ in range(8)]
fixture(node, base=0)
run2 = [random.randint(-110, 126) for _ in range(8)]
print(run1); print(run2)

Three back-to-back invocations on this machine produced three different
exponent sequences, e.g. [97, -60, 98, -69, 102, -84, 119, 2] then
[80, -68, -47, 94, 0, 33, -74, 77].

Suggested fix

Add random.seed(seed) immediately after torch.manual_seed(seed) in
the fixture (and import random at the top). PR follows.