Exp4State
@Serializable
@SerialName(value = "Exp4State")
Snapshot of com.eignex.kumulant.bandit.contextual.Exp4Bandit's state: the per-expert exponential weights. The bandit's state is over experts (not arms), so it surfaces via Snapshotable rather than the com.eignex.kumulant.bandit.PerArmBandit per-arm convenience.