Fix PotionContentsComponent and InstrumentComponent serialization for 1.20.6

Both components had incorrect Parse/Serialize implementations that would
cause packet deserialization misalignment when encountered in-game.

PotionContentsComponent (3 bugs):
- Serialize unconditionally wrote VarInt(PotionId) and Int(CustomColor)
  even when HasPotionId/HasCustomColor was false. The official format
  (PotionContents.STREAM_CODEC) uses Optional encoding: Bool(hasValue)
  followed by the value only when true. The extra bytes caused all
  subsequent fields in the packet to be read at wrong offsets.
- Serialize omitted the VarInt(count) prefix for the custom effects list.
  The official codec uses ByteBufCodecs.list() which always writes a
  VarInt count header before the list elements.
- Also fixed typo: PotiononId -> PotionId.

InstrumentComponent (3 bugs):
- The official Instrument.STREAM_CODEC uses ByteBufCodecs.holder() which
  encodes as VarInt(holderId): 0 = inline data, N>0 = registry ref (N-1).
  The SoundEvent field inside uses the same holder pattern. The old code
  unconditionally read SoundName (ResourceLocation) and HasFixedRange/
  FixedRange even when SoundEventHolderId != 0 (registry reference case
  has no inline data).
- UseDuration was read/written as Float, but the official codec uses
  ByteBufCodecs.VAR_INT. This caused a 4-byte vs variable-length
  mismatch that would shift all subsequent data.
- HasFixedRange was read unconditionally when SoundEventHolderId == 0,
  but FixedRange was also read unconditionally. The official SoundEvent
  DIRECT_STREAM_CODEC uses Optional<Float> encoding: Bool(hasValue)
  followed by Float only when true.

These components are used for potion items and goat horns respectively.
Verified against official 1.20.6 decompiled source:
- net.minecraft.world.item.alchemy.PotionContents (STREAM_CODEC)
- net.minecraft.world.item.Instrument (STREAM_CODEC/DIRECT_STREAM_CODEC)
- net.minecraft.sounds.SoundEvent (STREAM_CODEC/DIRECT_STREAM_CODEC)
- net.minecraft.network.codec.ByteBufCodecs (holder/optional/list)

Made-with: Cursor

MinecraftClient/Protocol/Handlers/StructuredComponents/Components/1_20_6/PotionContentsComponent.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Collections.Generic;
 using MinecraftClient.Inventory.ItemPalettes;
 using MinecraftClient.Protocol.Handlers.StructuredComponents.Components.Subcomponents;
@@ -11,21 +10,23 @@ public class PotionContentsComponent(DataTypes dataTypes, ItemPalette itemPalett
     : StructuredComponent(dataTypes, itemPalette, subComponentRegistry)
 {
     public bool HasPotionId { get; set; }
-    public int PotiononId { get; set; }
+    public int PotionId { get; set; }
     public bool HasCustomColor { get; set; }
     public int CustomColor { get; set; }
-    public int NumberOfCustomEffects { get; set; }
     public List<PotionEffectSubComponent> Effects { get; set; } = new();
     
     public override void Parse(Queue<byte> data)
     {
         HasPotionId = dataTypes.ReadNextBool(data);
-        PotiononId = HasPotionId ? dataTypes.ReadNextVarInt(data) : 0; // TODO: Find from the registry
+        if (HasPotionId)
+            PotionId = dataTypes.ReadNextVarInt(data);
+
         HasCustomColor = dataTypes.ReadNextBool(data);
-        CustomColor = HasCustomColor ? dataTypes.ReadNextInt(data) : 0; // TODO: Find from the registry
-        NumberOfCustomEffects = dataTypes.ReadNextVarInt(data);
-        
-        for(var i = 0; i < NumberOfCustomEffects; i++)
+        if (HasCustomColor)
+            CustomColor = dataTypes.ReadNextInt(data);
+
+        var numberOfEffects = dataTypes.ReadNextVarInt(data);
+        for (var i = 0; i < numberOfEffects; i++)
             Effects.Add((PotionEffectSubComponent)subComponentRegistry.ParseSubComponent(SubComponents.PotionEffect, data));
     }
 
@@ -33,19 +34,17 @@ public class PotionContentsComponent(DataTypes dataTypes, ItemPalette itemPalett
     {
         var data = new List<byte>();
         data.AddRange(DataTypes.GetBool(HasPotionId));
-        data.AddRange(DataTypes.GetVarInt(PotiononId));
-        data.AddRange(DataTypes.GetBool(HasCustomColor));
-        data.AddRange(DataTypes.GetInt(CustomColor));
+        if (HasPotionId)
+            data.AddRange(DataTypes.GetVarInt(PotionId));
 
-        if (NumberOfCustomEffects > 0)
-        {
-            if(Effects.Count != NumberOfCustomEffects)
-                throw new ArgumentNullException($"Can not serialize PotionContentsComponentComponent1206 due to NumberOfCustomEffects being different from the count of elements in the Effects list!");
-            
-            foreach(var effect in Effects)
-                data.AddRange(effect.Serialize());
-        }
+        data.AddRange(DataTypes.GetBool(HasCustomColor));
+        if (HasCustomColor)
+            data.AddRange(DataTypes.GetInt(CustomColor));
+
+        data.AddRange(DataTypes.GetVarInt(Effects.Count));
+        foreach (var effect in Effects)
+            data.AddRange(effect.Serialize());
         
         return new Queue<byte>(data);
     }
-}
+}