feat(runtime): own initial create residence transaction

tests/AcDream.Core.Tests/Physics/MotionSequenceGateTests.cs

@@ -118,6 +118,35 @@ public class PhysicsTimestampGateTests
         Assert.True(gate.TryAcceptMovementEvent(4, 0x9011, 2));
     }
 
+    [Fact]
+    public void PreviewCreateObject_MatchesSeedDispositionWithoutMutation()
+    {
+        var gate = new PhysicsTimestampGate();
+
+        Assert.Equal(CreateObjectTimestampDisposition.InitialGeneration,
+            gate.PreviewCreateObject(instance: 7));
+        Assert.Equal(CreateObjectTimestampDisposition.InitialGeneration,
+            gate.SeedForCreateObject(10, 20, 30, 40, 50, 60, 70, 80, 7));
+
+        Assert.Equal(CreateObjectTimestampDisposition.ExistingGeneration,
+            gate.PreviewCreateObject(instance: 7));
+        Assert.Equal(CreateObjectTimestampDisposition.NewGeneration,
+            gate.PreviewCreateObject(instance: 8));
+        Assert.Equal(CreateObjectTimestampDisposition.StaleGeneration,
+            gate.PreviewCreateObject(instance: 6));
+
+        // Preview is observational: all timestamp channels still compare
+        // against the original instance-seven seed afterward.
+        Assert.True(gate.TryAcceptMovementEvent(
+            instance: 7,
+            movement: 21,
+            serverControlledMove: 60));
+        Assert.False(gate.TryAcceptMovementEvent(
+            instance: 8,
+            movement: 22,
+            serverControlledMove: 60));
+    }
+
     [Fact]
     public void SameGenerationCreateObject_MixedChannelsAreAcceptedIndependently()
     {