fix: align animation pacing and transforms with native

engine/Age.Engine.Tests/FrameClockTests.cs

@@ -20,10 +20,47 @@ public class FrameClockTests
     }
 
     [Fact]
-    public void EffectiveBudget_ScalesBySpeed_AndFloorsAtOne()
+    public void Advance_RetainsFractionalMillisecondsAtSlowSpeed()
     {
-        Assert.Equal(30,  new FrameClock { OpsPerFrame = 30, Speed = 1.0 }.EffectiveBudget);
-        Assert.Equal(120, new FrameClock { OpsPerFrame = 30, Speed = 4.0 }.EffectiveBudget);
-        Assert.Equal(1,   new FrameClock { OpsPerFrame = 0,  Speed = 1.0 }.EffectiveBudget);
+        var c = new FrameClock { Speed = 0.1 };
+        for (int i = 0; i < 10; i++) c.Advance(1.0 / 144.0);
+        Assert.Equal(6, c.NowMs);
+    }
+
+    [Fact]
+    public void WallClockPacer_RateDoesNotDependOnRenderCallbackCount()
+    {
+        static long Simulate(int callbacks)
+        {
+            var c = new FrameClock();
+            var p = new WallClockOpPacer(c);
+            long ops = 0;
+            p.OpcodeCompleted(); ops++;
+            for (int frame = 0; frame < callbacks; frame++)
+            {
+                c.Advance(1.0 / callbacks);
+                while (p.CanRunNext) { p.OpcodeCompleted(); ops++; }
+            }
+            return ops;
+        }
+
+        long at60 = Simulate(60), at144 = Simulate(144), at240 = Simulate(240);
+        Assert.InRange(at60, 198, 202);
+        Assert.InRange(at144, 198, 202);
+        Assert.InRange(at240, 198, 202);
+        Assert.InRange(System.Math.Abs(at60 - at144), 0, 2);
+        Assert.InRange(System.Math.Abs(at60 - at240), 0, 2);
+    }
+
+    [Fact]
+    public void WallClockPacer_ResetDropsParkedTimeCredit()
+    {
+        var c = new FrameClock();
+        var p = new WallClockOpPacer(c);
+        p.OpcodeCompleted();
+        c.Advance(10);
+        p.Reset();
+        p.OpcodeCompleted();
+        Assert.False(p.CanRunNext);
     }
 }