feat(physics): port retail complete object frame pipeline

Restore the named-retail object update order across local, remote, static, projectile, animation, shadow, teleport, and effect lifetimes. Separate authoritative root commits from spatial rebucketing, preserve per-owner hook/FIFO ordering, and remove update-path allocations with exact lifecycle and residency gates.

Add deterministic conformance, adversarial lifetime, GUID-reuse, pending-cell, quaternion, timestamp, and allocation coverage. Release build is warning-free and all 6,446 tests pass with five intentional skips; retail, architecture, and adversarial reviews are clean.

Co-authored-by: OpenAI Codex <codex@openai.com>

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

@@ -104,6 +104,40 @@ public sealed class ProjectilePhysicsStepperTests
         Assert.Equal(50f, body.CachedVelocity.Y, 3);
     }
 
+    [Fact]
+    public void SplitQuantum_HoldsBeginFrameAcrossHookSlotThenCommitsCandidate()
+    {
+        var (engine, _) = BuildEmptyEngine();
+        var body = MakeBody(
+            new Vector3(12f, 10f, 2f),
+            new Vector3(10f, 0f, 0f));
+        var stepper = new ProjectilePhysicsStepper(engine);
+        Vector3 begin = body.Position;
+
+        ProjectileQuantumPreparation preparation = stepper.BeginQuantum(
+            body,
+            0.1f,
+            Cell,
+            ArrowSphere);
+
+        Assert.True(preparation.Simulated);
+        Assert.True(preparation.RequiresTransition);
+        Assert.Equal(begin, body.Position);
+        Assert.Equal(begin + Vector3.UnitX, preparation.CandidatePosition);
+
+        ProjectileAdvanceResult result = stepper.CompleteQuantum(
+            body,
+            preparation,
+            ArrowSphere,
+            ProjectileId);
+
+        Assert.True(result.Simulated);
+        Assert.InRange(
+            Vector3.Distance(begin + Vector3.UnitX, body.Position),
+            0f,
+            0.00001f);
+    }
+
     [Fact]
     public void Advance_GravityUsesFinalPhysicsState_NotParsedAcceleration()
     {