feat(net): port retail physics spawn and event timestamps

Parse the complete PhysicsDesc plus F754/F755 packets, correct every PhysicsState bit, and gate all nine retail update channels with generation-safe immutable snapshots. Preserve ForcePosition, teleport, placement, velocity, parent, pickup, delete, and same-generation CreateObject ordering from the named client.

Separate accepted logical lifecycle notifications from retained UI qualities, make GUID replacement and session reset clear every projection exactly once, and add packet, wraparound, malformed-input, parent FIFO, canonical-position, reconnect, and GUID-reuse conformance coverage.

Co-Authored-By: Codex <noreply@openai.com>

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

@@ -214,6 +214,11 @@ public sealed class ProjectileVfxPacketFixtureTests
         Assert.Equal(0xF754u, BinaryPrimitives.ReadUInt32LittleEndian(packet));
         Assert.Equal(0x50000042u, BinaryPrimitives.ReadUInt32LittleEndian(packet[4..]));
         Assert.Equal(0x33000099u, BinaryPrimitives.ReadUInt32LittleEndian(packet[8..]));
+
+        var parsed = PlayPhysicsScript.TryParse(packet);
+        Assert.Equal(new PlayPhysicsScript(0x50000042u, 0x33000099u), parsed);
+        Assert.Null(PlayPhysicsScript.TryParse(packet[..^1]));
+        Assert.Null(PlayPhysicsScript.TryParse([.. packet.ToArray(), 0]));
     }
 
     [Fact]
@@ -227,6 +232,28 @@ public sealed class ProjectileVfxPacketFixtureTests
         Assert.Equal(0xA5A5A5A5u, BinaryPrimitives.ReadUInt32LittleEndian(packet[8..]));
         Assert.Equal(0x7FC01234u, BinaryPrimitives.ReadUInt32LittleEndian(packet[12..]));
         Assert.True(float.IsNaN(BinaryPrimitives.ReadSingleLittleEndian(packet[12..])));
+
+        var parsed = PlayPhysicsScriptType.TryParse(packet);
+        Assert.NotNull(parsed);
+        Assert.Equal(0x50000042u, parsed.Value.Guid);
+        Assert.Equal(0xA5A5A5A5u, parsed.Value.RawScriptType);
+        Assert.Equal(0x7FC01234u, BitConverter.SingleToUInt32Bits(parsed.Value.Intensity));
+        Assert.Null(PlayPhysicsScriptType.TryParse(packet[..^1]));
+        Assert.Null(PlayPhysicsScriptType.TryParse([.. packet.ToArray(), 0]));
+    }
+
+    [Theory]
+    [InlineData(0x7F800000u)]
+    [InlineData(0xFF800000u)]
+    public void TypedF755_PreservesInfiniteIntensityBits(uint intensityBits)
+    {
+        byte[] packet = ProjectileVfxPacketFixtures.TypedF755UnknownNaN.ToArray();
+        BinaryPrimitives.WriteUInt32LittleEndian(packet.AsSpan(12), intensityBits);
+
+        var parsed = PlayPhysicsScriptType.TryParse(packet);
+
+        Assert.NotNull(parsed);
+        Assert.Equal(intensityBits, BitConverter.SingleToUInt32Bits(parsed.Value.Intensity));
     }
 
     [Fact]
@@ -248,6 +275,25 @@ public sealed class ProjectileVfxPacketFixtureTests
         Assert.Equal((ushort)0xFFF8, parsed.Value.PositionSequence);
         Assert.Equal((ushort)0xFFF9, parsed.Value.MovementSequence);
         Assert.Equal((ushort)0x0000, parsed.Value.InstanceSequence);
+
+        var physics = Assert.IsType<PhysicsSpawnData>(parsed.Value.Physics);
+        Assert.Equal(0x00000748u, physics.RawState);
+        Assert.True(physics.State.HasFlag(AcDream.Core.Physics.PhysicsStateFlags.Missile));
+        Assert.Equal(0x20000014u, physics.SoundTableId);
+        Assert.Equal(0x34000005u, physics.PhysicsScriptTableId);
+        Assert.Equal(new PhysicsAttachment(0x50000010u, 3u), physics.Parent);
+        Assert.Equal([new PhysicsAttachment(0x50000011u, 4u)],
+            physics.Children!.Value.ToArray());
+        Assert.Equal(0.25f, physics.Translucency);
+        Assert.Equal(new System.Numerics.Vector3(10f, 20f, 30f), physics.Velocity);
+        Assert.Equal(new System.Numerics.Vector3(1f, 2f, 3f), physics.Acceleration);
+        Assert.Equal(new System.Numerics.Vector3(0.1f, 0.2f, 0.3f), physics.AngularVelocity);
+        Assert.Equal(0xA5A5A5A5u, physics.DefaultScriptType);
+        Assert.Equal(0x7FC01234u,
+            BitConverter.SingleToUInt32Bits(physics.DefaultScriptIntensity!.Value));
+        Assert.Equal(new PhysicsTimestamps(
+            0xFFF8, 0xFFF9, 0xFFFA, 0xFFFB, 0xFFFC,
+            0xFFFD, 0xFFFE, 0xFFFF, 0x0000), physics.Timestamps);
     }
 
     [Fact]
@@ -264,6 +310,10 @@ public sealed class ProjectileVfxPacketFixtureTests
         Assert.Equal(0u, animation.Value.PlacementId);
         Assert.Equal((ushort)0x1108, movement.Value.InstanceSequence);
         Assert.Equal((ushort)0x1108, animation.Value.InstanceSequence);
+        Assert.NotNull(movement.Value.Physics!.Value.Movement);
+        Assert.True(movement.Value.Physics.Value.Movement!.Value.RawData.IsEmpty);
+        Assert.Null(movement.Value.Physics.Value.Movement!.Value.IsAutonomous);
+        Assert.Equal(0u, animation.Value.Physics!.Value.AnimationFrame);
     }
 
     [Fact]
@@ -277,7 +327,24 @@ public sealed class ProjectileVfxPacketFixtureTests
         Assert.Equal(0u, BinaryPrimitives.ReadUInt32LittleEndian(present[20..]));
         Assert.Equal(0u, BinaryPrimitives.ReadUInt32LittleEndian(absent[12..]));
         Assert.Equal(present.Length, absent.Length + sizeof(uint));
-        Assert.NotNull(CreateObject.TryParse(present));
-        Assert.NotNull(CreateObject.TryParse(absent));
+        var parsedPresent = CreateObject.TryParse(present);
+        var parsedAbsent = CreateObject.TryParse(absent);
+        Assert.NotNull(parsedPresent);
+        Assert.NotNull(parsedAbsent);
+        Assert.Equal(0u, parsedPresent.Value.Physics!.Value.PhysicsScriptTableId);
+        Assert.Null(parsedAbsent.Value.Physics!.Value.PhysicsScriptTableId);
+    }
+
+    [Fact]
+    public void GoldenCreateObject_RejectsEveryTruncationInsidePhysicsDesc()
+    {
+        byte[] packet = ProjectileVfxPacketFixtures.GoldenCreateObjectProjectilePhysicsFields;
+
+        // This fixture's PhysicsDesc ends at byte 168. Every shorter prefix
+        // cuts either a gated field or the mandatory nine-timestamp tail.
+        for (int length = 20; length < 168; length++)
+            Assert.Null(CreateObject.TryParse(packet.AsSpan(0, length)));
+
+        Assert.NotNull(CreateObject.TryParse(packet.AsSpan(0, 168)));
     }
 }