optim/sweep.py: ProcessPoolExecutor workers sample+evaluate genomes in
parallel; each result (feasible or not) is pushed through the
queue-backed single writer built in Stage 5. Verified with real
multiprocessing (not mocks): 12-run sweep across 2 worker processes
lands all 12 rows in SQLite with parseable genome/summary JSON, and two
independent sweeps with the same seed produce byte-identical results.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
