Phase 2: customers paying in coin (CRC/CRT/CRA/PSC), taint from stolen goods

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

tests/Decentralized.Domain.Tests/Program.cs

@@ -488,6 +488,16 @@ internal static class Program
             Check(Near(back.Market.Price, m.Price, 1e-9), "读回后继续推进，行情与原来完全相同");
         });
 
+        Test("用币付款：派系对应的币、按币价换算、污点与成本", () =>
+        {
+            var w = new Wallet { Address = "t" };
+            Check(CoinPayment.AssetFor("FACTION_BLACK_MARKET") == Assets.CRT && CoinPayment.AssetFor("FACTION_SECURITY") == null, "派系对应的币");
+            double q = CoinPayment.Receive(w, Assets.CRT, 200, 0.5, 40);
+            Check(Near(q, 400, 1e-9) && Near(w.Get(Assets.CRT), 400, 1e-9), "按币价换算数量");
+            Check(Near(w.Taint, 80, 1e-9) && Near(w.Basis, 200, 1e-9), "污点 = 货值 × 热度%，成本 = 货值");
+            Check(CoinPayment.Receive(w, Assets.CRC, 0, 1, 10) == 0, "零金额不收");
+        });
+
         Console.WriteLine($"\n{_passed} 通过，{_failed} 失败");
         return _failed == 0 ? 0 : 1;
     }