feat: add MC 1.21.5 (protocol 770) support

Full protocol adaptation for Minecraft 1.21.5:

- Protocol version mapping: 770 -> 1.21.5
- Packet palette: AddExperienceOrb removed (S2C), TestInstanceBlockStatus
  added (S2C), SetTestBlock and TestInstanceBlockAction added (C2S)
- Entity metadata palette: 5 new serializer types (OptionalLivingEntityReference,
  CowVariant, WolfSoundVariant, PigVariant, ChickenVariant), OPTIONAL_UUID
  replaced by OPTIONAL_LIVING_ENTITY_REFERENCE
- Item palette: 11 new items (Bush, FireflyBush, DryShortGrass, DryTallGrass,
  Wildflowers, LeafLitter, CactusFlower, TestBlock, TestInstanceBlock,
  BlueEgg, BrownEgg)
- Entity palette: Potion split into SplashPotion and LingeringPotion
- Block palette: 9 new blocks (bush, cactus_flower, firefly_bush, leaf_litter,
  short_dry_grass, tall_dry_grass, test_block, test_instance_block, wildflowers)
- Structured components: 31 new components including tooltip_display, weapon,
  blocks_attacks, potion_duration_scale, provides_trim_material,
  provides_banner_patterns, break_sound, and 25 entity variant components;
  unbreakable changed from Bool to Unit; instrument changed to EitherHolder

Made-with: Cursor

MinecraftClient/Mapping/EntityMetaDataType.cs

@@ -26,6 +26,10 @@ public enum EntityMetaDataType
     Direction,
     OptionalUuid,
     /// <summary>
+    /// Boolean + UUID (1.21.5+, replaces OptionalUuid)
+    /// </summary>
+    OptionalLivingEntityReference,
+    /// <summary>
     /// VarInt
     /// </summary>
     BlockId,
@@ -55,9 +59,25 @@ public enum EntityMetaDataType
     /// <summary>
     /// VarInt (1.20.6+)
     /// </summary>
+    CowVariant,
+    /// <summary>
+    /// VarInt (1.20.6+)
+    /// </summary>
     WolfVariant,
+    /// <summary>
+    /// VarInt (1.21.5+)
+    /// </summary>
+    WolfSoundVariant,
     FrogVariant,
     /// <summary>
+    /// VarInt (1.21.5+)
+    /// </summary>
+    PigVariant,
+    /// <summary>
+    /// VarInt (1.21.5+)
+    /// </summary>
+    ChickenVariant,
+    /// <summary>
     /// String + Position
     /// </summary>
     GlobalPosition,