Stage 7.1: prediction markets (LMSR, event/faction/purity/price markets, insider check)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/Decentralized/Session.cs

@@ -33,6 +33,8 @@ namespace Decentralized
         public Staking Staking = new Staking();
         /// <summary>Poinbase 永续合约账本（保证金用 Poinbase 账户的 CRC）。</summary>
         public PerpBook Perps = new PerpBook();
+        /// <summary>预测市场：盘口、持仓、观测记录（下注资金用 Poinbase 账户的 CRC）。</summary>
+        public PredictBook Predict = new PredictBook();
         /// <summary>质押日息下调的新闻已经发过。</summary>
         public bool CraLowNews;
         public Network Network = new Network();