Seed entropy comes from bip39 -> rand::thread_rng -> getrandom(2), which
blocks until the kernel pool is initialized -- but that ordering was
invisible in logs on first-boot ISO flows where the seed is generated
early. MasterSeed::generate() now probes getrandom(GRND_NONBLOCK) and
logs whether the pool was already seeded (warn if it would block).
Also adds a regression test that 64 generated mnemonics are all unique
with sane word diversity, guarding against a fixed/seeded RNG ever
being wired into seed generation.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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