Move LOREM_genBlock and LOREM_genBuffer into the Rust CLI helper archive,
preserving the frozen word distribution, seeded sentence and paragraph layout,
tail filling, and C-compatible buffer ABI. Use per-call state so generation is
reentrant without changing the generated bytes.
Focused tests cover C reference vectors, distribution construction,
determinism, zero-sized null buffers, tiny tail-filled buffers, and continued
nonzero-fill generation.
Test Plan:
- cargo test --manifest-path rust/cli/Cargo.toml --no-default-features lorem::tests
- cargo clippy --manifest-path rust/cli/Cargo.toml --all-targets -- -D warnings
Refs: programs/lorem.c compatibility port
