Phase 2: CRT freeze during crackdowns (frozen balance, thaw, news, test entry)

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

src/Decentralized.Domain/Stablecoins.cs

@@ -49,6 +49,9 @@ namespace Decentralized.Domain
         public static double CrtFreezeChance(double blackMarketRep) =>
             Math.Max(0, Tuning.CrtFreezeBase - blackMarketRep * Tuning.CrtFreezePerRep);
 
+        /// <summary>镇压开始时是否冻结玩家的 CRT：按黑市声望，声望越低越容易被黑市"出卖"。</summary>
+        public static bool CrtFrozenByCrackdown(double blackMarketRep, Rng rng) => rng.Chance(CrtFreezeChance(blackMarketRep));
+
         public bool CraSubsidyLow => CraSubsidy <= Tuning.CraSubsidy0 * Tuning.CraSubsidyWarn;
 
         /// <summary>CRA 的预兆：外生螺旋的新闻已出，或补贴池告急（利率下调）。螺旋开始后不再算预兆。</summary>