InitBattle now emits Stable(master) as the shared effect seed and the master- shuffled deck as selfDeck; Swap emits each recipient's per-side IdxChange seed. BattleSession exposes + logs the master seed per battle for future replay. Updated lifecycle/dispatch/integration tests (deck assertions now permutation- based since selfDeck is shuffled). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>