fix(anim): Phase L.1c route creature actions and despawns

Handle retail ObjectDelete (0xF747) using CM_Physics::DispatchSB_DeleteObject 0x006AC6A0 / SmartBox::HandleDeleteObject 0x00451EA0 and ACE GameMessageDeleteObject so dead creatures are removed when corpses spawn.

Route action-class ForwardCommand values through AnimationCommandRouter/PlayAction instead of SetCycle so creature attack commands 0x51/0x52/0x53 survive the immediate Ready echo, matching CMotionTable::GetObjectSequence 0x00522860 / ACE MotionTable.GetObjectSequence.

Use server-authoritative UpdatePosition velocity, or observed server position delta for non-player entities when HasVelocity is absent, to reduce monster/NPC chase lag without applying player RUM prediction to server-controlled creatures.

tests/AcDream.Core.Net.Tests/Messages/DeleteObjectTests.cs

@@ -0,0 +1,39 @@
+using System.Buffers.Binary;
+using AcDream.Core.Net.Messages;
+using Xunit;
+
+namespace AcDream.Core.Net.Tests.Messages;
+
+public sealed class DeleteObjectTests
+{
+    [Fact]
+    public void RejectsWrongOpcode()
+    {
+        Span<byte> body = stackalloc byte[12];
+        BinaryPrimitives.WriteUInt32LittleEndian(body, 0xDEADBEEFu);
+
+        Assert.Null(DeleteObject.TryParse(body));
+    }
+
+    [Fact]
+    public void RejectsTruncated()
+    {
+        Assert.Null(DeleteObject.TryParse(ReadOnlySpan<byte>.Empty));
+        Assert.Null(DeleteObject.TryParse(new byte[9]));
+    }
+
+    [Fact]
+    public void ParsesGuidAndInstanceSequence()
+    {
+        Span<byte> body = stackalloc byte[12];
+        BinaryPrimitives.WriteUInt32LittleEndian(body, DeleteObject.Opcode);
+        BinaryPrimitives.WriteUInt32LittleEndian(body.Slice(4), 0x80000439u);
+        BinaryPrimitives.WriteUInt16LittleEndian(body.Slice(8), 0x1234);
+
+        var parsed = DeleteObject.TryParse(body);
+
+        Assert.NotNull(parsed);
+        Assert.Equal(0x80000439u, parsed!.Value.Guid);
+        Assert.Equal((ushort)0x1234, parsed.Value.InstanceSequence);
+    }
+}

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

@@ -1313,6 +1313,45 @@ public sealed class AnimationSequencerTests
         Assert.Equal(99f, fr[0].Origin.X, 1);
     }
 
+    [Fact]
+    public void PlayAction_ActionSurvivesImmediateReadyCycleEcho()
+    {
+        // ACE broadcasts creature attacks as Action-class ForwardCommand
+        // values followed by Ready. Retail keeps currState.Substate at Ready
+        // while the action link drains, so the Ready echo must not abort the
+        // in-flight swing.
+        const uint Style        = 0x003Du;
+        const uint IdleMotion   = 0x41000003u;
+        const uint AttackMotion = 0x10000052u;
+        const uint IdleAnimId   = 0x03000503u;
+        const uint AttackAnimId = 0x03000504u;
+
+        var setup = Fixtures.MakeSetup(1);
+        var mt = new MotionTable { DefaultStyle = (DRWMotionCommand)Style };
+        int cycleKey = (int)((Style << 16) | (IdleMotion & 0xFFFFFFu));
+        mt.Cycles[cycleKey] = Fixtures.MakeMotionData(IdleAnimId, framerate: 10f);
+
+        int linkOuter = (int)((Style << 16) | (IdleMotion & 0xFFFFFFu));
+        var cmdData = new MotionCommandData();
+        cmdData.MotionData[(int)AttackMotion] = Fixtures.MakeMotionData(AttackAnimId, framerate: 10f);
+        mt.Links[linkOuter] = cmdData;
+
+        var loader = new FakeLoader();
+        loader.Register(IdleAnimId, Fixtures.MakeAnim(4, 1, Vector3.Zero, Quaternion.Identity));
+        loader.Register(AttackAnimId, Fixtures.MakeAnim(3, 1, new Vector3(12, 0, 0), Quaternion.Identity));
+
+        var seq = new AnimationSequencer(setup, mt, loader);
+        seq.SetCycle(Style, IdleMotion);
+        seq.PlayAction(AttackMotion);
+
+        seq.SetCycle(Style, IdleMotion);
+
+        var fr = seq.Advance(0.01f);
+        Assert.Single(fr);
+        Assert.Equal(12f, fr[0].Origin.X, 1);
+        Assert.Equal(IdleMotion, seq.CurrentMotion);
+    }
+
     [Fact]
     public void PlayAction_Modifier_ResolvesFromModifiersDict()
     {