fix: model gidx's family id as a nullable id and revert the serializer patch (#494)

#493 patched the serializer so a null sub-packet emits its discriminator with
the -1. That was the wrong level: NullableSerializer already carries the
splitter into the null branch for a nullable value, and gidx only needed the
engine change because the packet was modelled wrong.

The server gidx declared FamilyIdentifier as a two-field sub-packet rendering
serverId.familyId. The client gidx next to it already declares a plain
long FamilyId at the same index, and a capture writes a single id. Flattened to
long?, so a null family now serialises as "gidx 1 741328 -1 - 0" through the
ordinary nullable path with no serializer change at all.

ScnPacket index 9 was missing the SpecialSeparator its three siblings carry, so
the boots slot went out as three space-separated fields instead of dotted.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: erwan-joly

src/NosCore.Packets/Serializer.cs

@@ -273,7 +273,7 @@ private Expression PacketSerializer(Expression injectedPacket, PacketIndexAttrib
 
             return Expression.Condition(
                 Expression.Equal(specificTypeExpression, Expression.Constant(null, typeof(object))),
-                Expression.Constant(indexAttr.IsOptional ? null : $"{discriminator}-1", typeof(object)),
+                Expression.Constant(indexAttr.IsOptional ? null : "-1", typeof(object)),
                 Expression.Convert(propExp, typeof(object))
             );
         }

src/NosCore.Packets/ServerPackets/Families/GidxFamilySubPacket.cs

@@ -20,8 +20,8 @@ public class GidxPacket : PacketBase
         [PacketIndex(1)]
         public long VisualId { get; set; }
 
-        [PacketIndex(2, SpecialSeparator = ".")]
-        public GidxFamilySubPacket? FamilyIdentifier { get; set; }
+        [PacketIndex(2)]
+        public long? FamilyId { get; set; }
 
         [PacketIndex(3)]
         public string? FamilyName { get; set; }

src/NosCore.Packets/ServerPackets/Families/GidxPacket.cs

@@ -42,7 +42,7 @@ public class ScnPacket : PacketBase
         [PacketIndex(8, SpecialSeparator = ".")]
         public ScEquipmentDetails? GauntletInstanceDetails { get; set; }
 
-        [PacketIndex(9)]
+        [PacketIndex(9, SpecialSeparator = ".")]
         public ScEquipmentDetails? BootsInstanceDetails { get; set; }
 
         [PacketIndex(10)]

src/NosCore.Packets/ServerPackets/Mates/ScnPacket.cs

@@ -34,6 +34,7 @@
 using NosCore.Shared.Enumerations;
 using System.Collections.Generic;
 using System.Linq;
+using ServerGidxPacket = NosCore.Packets.ServerPackets.Families.GidxPacket;
 
 namespace NosCore.Packets.Tests
 {
@@ -519,24 +520,39 @@ public void SerializeWithNullFirstParam()
                 packet);
         }
 
+        // gidx exists on both sides with different shapes, and the serializer keys on the simple
+        // type name, so the server one needs its own instance.
+        private static readonly ISerializer ServerSerializer =
+            new Serializer(new[] { typeof(ServerGidxPacket) });
+
+        [TestMethod]
+        public void SerializeGidxWithoutFamily()
+        {
+            var packet = ServerSerializer.Serialize(new ServerGidxPacket
+            {
+                VisualType = VisualType.Player,
+                VisualId = 741328,
+                FamilyId = null,
+                FamilyName = "-",
+                FamilyLevel = 0
+            });
+
+            Assert.AreEqual("gidx 1 741328 -1 - 0 ", packet);
+        }
+
         [TestMethod]
-        public void SerializeWithNullSubPacketKeepsTheSeparator()
+        public void SerializeGidxWithFamily()
         {
-            var packet = Serializer.Serialize(new ScnPacket
+            var packet = ServerSerializer.Serialize(new ServerGidxPacket
             {
-                PetId = 1,
-                NpcMonsterVNum = 319,
-                TransportId = 26719,
-                Level = 50,
-                Loyalty = 1000,
-                Experience = 1536,
-                WeaponInstanceDetails = new ScnPacket.ScEquipmentDetails { ItemId = 990 },
-                Name = "Kliff",
-                MorphId = -1
+                VisualType = VisualType.Player,
+                VisualId = 741328,
+                FamilyId = 5052,
+                FamilyName = "-Nemesis-",
+                FamilyLevel = 7
             });
 
-            Assert.IsTrue(packet.StartsWith("sc_n 1 319 26719 50 1000 1536 990.0.0 -1 -1 -1 "),
-                $"the -1 of a null sub-packet must not be glued to the field before it: {packet}");
+            Assert.AreEqual("gidx 1 741328 5052 -Nemesis- 7 ", packet);
         }
 
         [TestMethod]