Used-hardware dealer customer and GPU appraisal registration

A scav-type seller visits now and then with three to five used cards. An
honest dealer sells at true value, a middleman adds 8%, a scammer mixes in
fakes (relabelled cheap chips) priced at 90% of the labelled model's value.
The markup is a client-temporary item feature, so a bought card is only
worth its real value. Cards are registered as appraisal items; the correct
value is the same function as the sale value.

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

tests/Decentralized.Domain.Tests/Program.cs

@@ -335,6 +335,29 @@ internal static class Program
             Check(Near(dr.Received, 900 * (1 - Tuning.ExchangeFee), 1e-6), "CRC 脱锚时按市价兑出");
         });
 
+        Test("二手贩子：老实人没有假卡；骗子按标称价九折报价；假卡芯片至少便宜一半；买下后只值真实价值", () =>
+        {
+            var rng = new Rng(7);
+            int fakes = 0, cards = 0;
+            for (int i = 0; i < 300; i++)
+                foreach (var c in UsedDealers.Cards(DealerKind.Honest, 40, rng))
+                    Check(c.FakeOf == null && c.MarkupPct == 0, "老实人的卡是真卡且按真实价值");
+            for (int i = 0; i < 300; i++)
+                foreach (var c in UsedDealers.Cards(DealerKind.Scammer, 40, rng))
+                {
+                    cards++;
+                    if (c.FakeOf == null) continue;
+                    fakes++;
+                    var u = new Unit { Model = c.Model, FakeOf = c.FakeOf, Health = c.Health };
+                    Check(Hardware.Specs[c.FakeOf].Price * 2 <= Hardware.Specs[c.Model].Price, "假卡的芯片至少便宜一半");
+                    long shown = (long)Math.Round(CardValue.True(u) * (1 + c.MarkupPct / 100.0));
+                    Check(Math.Abs(shown - CardValue.Of(c.Model, c.Health) * UsedDealers.ScamDiscount) <= CardValue.True(u) * 0.01 + 1, "柜台价约等于标称价九折");
+                    Check(c.MarkupPct > 0, "假卡的柜台价高于真实价值");
+                }
+            Check(fakes > cards * 0.2 && fakes < cards * 0.5, $"骗子的假卡占两成多（入门卡便宜到没法冒充）：{fakes}/{cards}");
+            Check(UsedDealers.Pool(5).All(m => Dealer.Basic.Contains(m)) && UsedDealers.Pool(30).Contains("RZX90"), "型号按天数放开");
+        });
+
         Test("杰克逊博士：没有矿架必上一个；基础卡每次两张；进阶第 10 天起、旗舰第 30 天起；特供货第 20 天起必有旗舰", () =>
         {
             var rng = new Rng(11);