fix: align animation pacing and transforms with native

engine/Age.Engine/Hosting/FrameClock.cs

@@ -1,23 +1,75 @@
 namespace Age.Engine.Hosting;
 
-/// <summary>Host-owned virtual clock + per-frame op budget. Pure (no threading): the Godot host
-/// advances it once per rendered frame and consults it to pace the VM. The one <see cref="Speed"/>
-/// factor is the future (unwired) Ctrl fast-forward multiplier — scaling it scales the throttle
-/// budget, sleeps, and the anim tween together. See docs/superpowers/specs/2026-07-08-frame-stepped-vm-design.md.</summary>
+/// <summary>Host-owned virtual clock. Godot advances it from real elapsed time; VM pacing, sleeps, and
+/// retained graphics all consume this same timebase. Fractional milliseconds are retained so diagnostic
+/// slow motion does not stall on high-refresh displays.</summary>
 public sealed class FrameClock
 {
-    /// <summary>Monotonic virtual time in milliseconds (scaled by Speed).</summary>
-    public long NowMs { get; private set; }
+    private long _nowMs;
+    private double _fractionalMs;
 
-    /// <summary>Speed multiplier. 1.0 = normal. The future Ctrl hook (ADV-scoped); leave at 1.0 for now.</summary>
+    /// <summary>Monotonic virtual time in milliseconds (scaled by Speed).</summary>
+    public long NowMs => System.Threading.Interlocked.Read(ref _nowMs);
+
+    /// <summary>Speed multiplier. 1.0 = normal. A lower diagnostic value slows VM progress, sleeps, and
+    /// graphics together; a future ADV-scoped Ctrl hook can drive the same seam.</summary>
     public double Speed = 1.0;
 
-    /// <summary>Base per-frame interpreter op budget (tunable by eye; ~30 ≈ 1,800 ops/sec at 60fps).</summary>
-    public int OpsPerFrame = 30;
+    /// <summary>Native normal-playback interpreter cadence. The old 1,800 figure counted calls to
+    /// vm_operand_fetch, not completed opcodes. A live 1,890 ms transform section executes about 407
+    /// port opcodes. A normal-speed replay at 215/s retained the object for 1,798 ms; 200/s reaches
+    /// the native 1,890 ms endpoint before the same teardown path.</summary>
+    public double OpsPerSecond = 200.0;
 
     /// <summary>Advance the clock by one rendered frame's real delta (seconds), scaled by Speed.</summary>
-    public void Advance(double realDeltaSeconds) => NowMs += (long)(realDeltaSeconds * 1000.0 * Speed);
-
-    /// <summary>Ops the VM may run before yielding a frame, scaled by Speed (min 1).</summary>
-    public int EffectiveBudget => System.Math.Max(1, (int)System.Math.Round(OpsPerFrame * Speed));
+    public void Advance(double realDeltaSeconds)
+    {
+        double scaled = realDeltaSeconds * 1000.0 * Speed + _fractionalMs;
+        long whole = (long)System.Math.Floor(scaled);
+        _fractionalMs = scaled - whole;
+        if (whole > 0) System.Threading.Interlocked.Add(ref _nowMs, whole);
+    }
+}
+
+/// <summary>Pure wall-clock opcode rate limiter. The VM thread records completed opcodes and waits whenever
+/// it has consumed the allowance earned from <see cref=FrameClock.NowMs/>. Reset after a blocking wait so
+/// parked time never turns into a catch-up burst.</summary>
+public sealed class WallClockOpPacer
+{
+    private readonly FrameClock _clock;
+    private bool _started;
+    private long _epochMs;
+    private long _completed;
+
+    public WallClockOpPacer(FrameClock clock) => _clock = clock;
+
+    public void OpcodeCompleted()
+    {
+        if (!_started)
+        {
+            _started = true;
+            _epochMs = _clock.NowMs;
+            _completed = 0;
+        }
+        _completed++;
+    }
+
+    /// <summary>Whether the next opcode may execute at the clock's current time.</summary>
+    public bool CanRunNext
+    {
+        get
+        {
+            if (!_started) return true;
+            long elapsed = System.Math.Max(0, _clock.NowMs - _epochMs);
+            long allowance = 1 + (long)System.Math.Floor(elapsed * _clock.OpsPerSecond / 1000.0);
+            return _completed < allowance;
+        }
+    }
+
+    public void Reset()
+    {
+        _started = false;
+        _epochMs = 0;
+        _completed = 0;
+    }
 }