Domain core: seeded RNG, asset registry, wallets, AMM pairs, mining

Pure logic layer with no game references: xoshiro128** RNG with savable
state, asset registry (PSC, CRC, CRT, CRA, SPARK, Ponero), wallets whose
taint and cost basis move with transfers, constant-product pools with
nightly reversion, and mining (Probidia/PMD GPUs, RatDigg ASICs, network
hash response, halving, wear and sudden death). 35 checks pass.

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

src/Decentralized.Domain/Amm.cs

@@ -0,0 +1,84 @@
+using System;
+
+namespace Decentralized.Domain
+{
+    public enum Venue { Exchange, Dex, Darknet }
+
+    /// <summary>
+    /// 一个交易对 = 一个恒定乘积池（x·y = k）。Base 是被交易的币，Quote 是计价币；价格 = Quote 储备 / Base 储备。
+    /// 每个交易对各有深度；夜间由 NPC 套利者把价格按比例拉向目标价。
+    /// </summary>
+    public sealed class Pool
+    {
+        public string Base, Quote;
+        public Venue Venue;
+        public double BaseReserve, QuoteReserve;
+        public double Fee;
+
+        public string Id => $"{Venue}:{Base}/{Quote}";
+
+        public double Price => QuoteReserve / BaseReserve;
+
+        public static Pool Create(Venue venue, string baseAsset, string quote, double price, double quoteDepth, double fee) =>
+            new Pool { Venue = venue, Base = baseAsset, Quote = quote, QuoteReserve = quoteDepth, BaseReserve = quoteDepth / price, Fee = fee };
+
+        /// <summary>预估：卖出 baseIn 个 Base 能得到多少 Quote（不改池子）。</summary>
+        public double QuoteOut(double baseIn)
+        {
+            double x = BaseReserve + baseIn * (1 - Fee);
+            return QuoteReserve - BaseReserve * QuoteReserve / x;
+        }
+
+        /// <summary>预估：花 quoteIn 个 Quote 能买到多少 Base（不改池子）。</summary>
+        public double BaseOut(double quoteIn)
+        {
+            double y = QuoteReserve + quoteIn * (1 - Fee);
+            return BaseReserve - BaseReserve * QuoteReserve / y;
+        }
+
+        /// <summary>卖出 Base，返回得到的 Quote。手续费留在池里。</summary>
+        public double SellBase(double baseIn)
+        {
+            if (baseIn <= 0) return 0;
+            double out_ = QuoteOut(baseIn);
+            BaseReserve += baseIn;
+            QuoteReserve -= out_;
+            return out_;
+        }
+
+        /// <summary>用 Quote 买入 Base，返回得到的 Base。</summary>
+        public double BuyBase(double quoteIn)
+        {
+            if (quoteIn <= 0) return 0;
+            double out_ = BaseOut(quoteIn);
+            QuoteReserve += quoteIn;
+            BaseReserve -= out_;
+            return out_;
+        }
+
+        /// <summary>一笔交易的价格冲击（交易后价格相对交易前的变化比例）。</summary>
+        public double ImpactOfBuy(double quoteIn)
+        {
+            double before = Price;
+            double y = QuoteReserve + quoteIn * (1 - Fee);
+            double x = BaseReserve * QuoteReserve / y;
+            return (y / x) / before - 1;
+        }
+
+        /// <summary>
+        /// 夜间：价格在对数空间里向 target 靠拢 rate 的比例，同时把 Quote 一侧的深度重设为 quoteDepth。
+        /// </summary>
+        public void Revert(double target, double rate, double quoteDepth)
+        {
+            double lp = Math.Log(Price);
+            lp += rate * (Math.Log(target) - lp);
+            SetPrice(Math.Exp(lp), quoteDepth);
+        }
+
+        public void SetPrice(double price, double quoteDepth)
+        {
+            QuoteReserve = quoteDepth;
+            BaseReserve = quoteDepth / price;
+        }
+    }
+}