domain_rand_episode_starts used constant seed (i, 0, 9999) producing
identical episode starting bars every epoch. With deterministic starts
and alternating weight updates, the OOS Sharpe oscillated perfectly
between +0.85 and -1.0. Adding epoch to the Philox hash key diversifies
starting positions across epochs.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>