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>