落地无头规则引擎与局内内容，便于命令行复现对战。

规则、卡包与测试放在同一套核心里，避免表现层自行结算。

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/Game.Core.Tests/PhaseATests.cs

@@ -0,0 +1,54 @@
+using CardGame.Core;
+using Xunit;
+
+namespace Game.Core.Tests;
+
+public sealed class PhaseATests
+{
+    [Fact]
+    public void Clone_is_independent()
+    {
+        var state = new GameState(seed: 1) { Catalog = Cards.Catalog };
+        state.Players[0].Life = 12;
+        var clone = RulesEngine.CloneState(state);
+        clone.Players[0].Life = 7;
+        Assert.Equal(12, state.Players[0].Life);
+        Assert.Equal(7, clone.Players[0].Life);
+    }
+
+    [Fact]
+    public void Rng_is_deterministic_for_same_seed()
+    {
+        var a = new GameRng(42);
+        var b = new GameRng(42);
+        Assert.Equal(a.NextUInt32(), b.NextUInt32());
+        Assert.Equal(a.NextInt(10), b.NextInt(10));
+    }
+
+    [Fact]
+    public void EndTurn_passes_priority_and_base_field_supplies()
+    {
+        var state = MatchSetup.Create(
+            7,
+            Cards.Repeat(Cards.Wisp, 10),
+            Cards.Repeat(Cards.Wisp, 10),
+            Cards.Catalog,
+            shuffle: false);
+        Assert.Equal(1, state.Players[0].Energy);
+        state = RulesEngine.Execute(state, new EndTurnAction(0));
+        Assert.Equal(1, state.ActivePlayerIndex);
+        Assert.Equal(1, state.Players[1].Energy);
+    }
+
+    [Fact]
+    public void GetLegalActions_offers_end_turn()
+    {
+        var state = MatchSetup.Create(
+            1,
+            Cards.Repeat(Cards.Wisp, 10),
+            Cards.Repeat(Cards.Wisp, 10),
+            Cards.Catalog,
+            shuffle: false);
+        Assert.Contains(RulesEngine.GetLegalActions(state), a => a is EndTurnAction);
+    }
+}