feat: add palettes and version constants for MC 1.21.2 (protocol 768)

Add item, entity, block, and metadata palettes for Minecraft 1.21.2:
- ItemPalette1212: 1375 items (42 new: pale oak set, colored bundles,
  creaking heart/spawn egg, banner patterns)
- EntityPalette1212: 150 entity types (boats split into per-wood-type
  entries, generic boat/chest_boat removed; added creaking,
  creaking_transient, pale oak boats)
- Palette1212 (blocks): 1084 block types with state IDs generated from
  official 1.21.2 data reports (24 new pale oak blocks, creaking heart,
  pale moss variants)
- EntityMetadataPalette: reuses 1206 (serializers unchanged in 1.21.2)

Updated version infrastructure:
- Protocol18.cs: MC_1_21_2_Version = 768, palette switch routing
- ProtocolHandler.cs: version mapping 1.21.2 <-> 768
- Program.cs: MCHighestVersion bumped to 1.21.2
- ItemType.cs, EntityType.cs, Material.cs: new enum entries

Note: packet palette, structured components, and protocol handler
changes for 1.21.2 are not yet implemented — this commit covers
palette/registry groundwork only.

Made-with: Cursor

MinecraftClient/Mapping/EntityType.cs

@@ -1,4 +1,4 @@
-namespace MinecraftClient.Mapping
+namespace MinecraftClient.Mapping
 {
     /// <summary>
     /// Represents Minecraft Entity Types
@@ -14,14 +14,20 @@
     /// </remarks>
     public enum EntityType
     {
+        AcaciaBoat,
+        AcaciaChestBoat,
         Allay,
         AreaEffectCloud,
         Armadillo,
         ArmorStand,
         Arrow,
         Axolotl,
+        BambooChestRaft,
+        BambooRaft,
         Bat,
         Bee,
+        BirchBoat,
+        BirchChestBoat,
         Blaze,
         BlockDisplay,
         Boat,
@@ -31,13 +37,19 @@
         Camel,
         Cat,
         CaveSpider,
+        CherryBoat,
+        CherryChestBoat,
         ChestBoat,
         ChestMinecart,
         Chicken,
         Cod,
         CommandBlockMinecart,
         Cow,
+        Creaking,
+        CreakingTransient,
         Creeper,
+        DarkOakBoat,
+        DarkOakChestBoat,
         Dolphin,
         Donkey,
         DragonFireball,
@@ -77,18 +89,26 @@
         Item,
         ItemDisplay,
         ItemFrame,
+        JungleBoat,
+        JungleChestBoat,
         LeashKnot,
         LightningBolt,
         Llama,
         LlamaSpit,
         MagmaCube,
+        MangroveBoat,
+        MangroveChestBoat,
         Marker,
         Minecart,
         Mooshroom,
         Mule,
+        OakBoat,
+        OakChestBoat,
         Ocelot,
         OminousItemSpawner,
         Painting,
+        PaleOakBoat,
+        PaleOakChestBoat,
         Panda,
         Parrot,
         Phantom,
@@ -117,6 +137,8 @@
         SpawnerMinecart,
         SpectralArrow,
         Spider,
+        SpruceBoat,
+        SpruceChestBoat,
         Squid,
         Stray,
         Strider,