Stress (round 4, snapshot10e): 5/5 pass.
h1: 4 CLIs on one project/HOME; sessions, writes.jsonl, snapshots all valid; no lost write, no lock/tmp files. h2: 12-way burst, all exit 0, no cross-talk; still no 429/529 (rate-limit path not exercised; environment). h3: 8 parallel modules, all tests pass, 28 versions match. h4: one resume wins the lock, the other refused with a clear message (by design). h5: 5 rapid messages processed in order, none lost/duplicated.
All multi-session costs equal the per-session sums.
