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.

src/AcDream.Core.Net/Messages/DeleteObject.cs

@@ -0,0 +1,39 @@
+using System.Buffers.Binary;
+
+namespace AcDream.Core.Net.Messages;
+
+/// <summary>
+/// Inbound <c>ObjectDelete</c> GameMessage (opcode <c>0xF747</c>).
+///
+/// <para>
+/// Retail dispatch path:
+/// <c>CM_Physics::DispatchSB_DeleteObject</c> 0x006AC6A0 reads guid from
+/// <c>buf+4</c> and instance sequence from <c>buf+8</c>, then calls
+/// <c>SmartBox::HandleDeleteObject</c> 0x00451EA0. ACE emits the same
+/// layout from <c>GameMessageDeleteObject</c>.
+/// </para>
+/// </summary>
+public static class DeleteObject
+{
+    public const uint Opcode = 0xF747u;
+
+    public readonly record struct Parsed(uint Guid, ushort InstanceSequence);
+
+    /// <summary>
+    /// Parse a 0xF747 body. <paramref name="body"/> must start with the
+    /// 4-byte opcode, matching every other parser in this namespace.
+    /// </summary>
+    public static Parsed? TryParse(ReadOnlySpan<byte> body)
+    {
+        if (body.Length < 10)
+            return null;
+
+        uint opcode = BinaryPrimitives.ReadUInt32LittleEndian(body.Slice(0, 4));
+        if (opcode != Opcode)
+            return null;
+
+        uint guid = BinaryPrimitives.ReadUInt32LittleEndian(body.Slice(4, 4));
+        ushort instanceSequence = BinaryPrimitives.ReadUInt16LittleEndian(body.Slice(8, 2));
+        return new Parsed(guid, instanceSequence);
+    }
+}

src/AcDream.Core.Net/WorldSession.cs

@@ -61,6 +61,16 @@ public sealed class WorldSession : IDisposable
     /// <summary>Fires when the session finishes parsing a CreateObject.</summary>
     public event Action<EntitySpawn>? EntitySpawned;
 
+    /// <summary>
+    /// Fires when the session parses a 0xF747 ObjectDelete game message.
+    /// Retail routes this through
+    /// <c>CM_Physics::DispatchSB_DeleteObject</c> 0x006AC6A0 →
+    /// <c>SmartBox::HandleDeleteObject</c> 0x00451EA0; ACE emits it when
+    /// an object leaves the world, including the living creature object
+    /// after its corpse is created.
+    /// </summary>
+    public event Action<DeleteObject.Parsed>? EntityDeleted;
+
     /// <summary>
     /// Payload for <see cref="MotionUpdated"/>: the server guid of the entity
     /// whose motion changed and its new server-side stance + forward command.
@@ -641,6 +651,12 @@ public sealed class WorldSession : IDisposable
                         parsed.Value.MotionTableId));
                 }
             }
+            else if (op == DeleteObject.Opcode)
+            {
+                var parsed = DeleteObject.TryParse(body);
+                if (parsed is not null)
+                    EntityDeleted?.Invoke(parsed.Value);
+            }
             else if (op == UpdateMotion.Opcode)
             {
                 // Phase 6.6: the server sends UpdateMotion (0xF74C) whenever an