feat: add MC 1.21.6 (protocol 771) version constants and enum values

- Add protocol 771 constant MC_1_21_6_Version in Protocol18.cs
- Register 1.21.6 in ProtocolHandler (version map, supported list)
- Extend upper-bound checks from MC_1_21_5 to MC_1_21_6
- Add 19 new ItemType entries (16 colored Harnesses, DriedGhast,
  HappyGhastSpawnEgg, MusicDiscTears)
- Add HappyGhast to EntityType enum
- Add DriedGhast to Material enum
- Add new packet types: Waypoint, ClearDialog, ShowDialog (clientbound),
  ChangeGameMode, CustomClickAction (serverbound),
  ClearDialog, ShowDialog (config clientbound),
  CustomClickAction (config serverbound)

Made-with: Cursor

MinecraftClient/Protocol/ProtocolHandler.cs

@@ -154,7 +154,7 @@ namespace MinecraftClient.Protocol
             {
                 4, 5, 47, 107, 108, 109, 110, 210, 315, 316, 335, 338, 340, 393, 401, 404, 477, 480, 485, 490, 498, 573,
                 575, 578, 735, 736, 751, 753, 754, 755, 756, 757, 758, 759, 760, 761, 762, 763, 764, 765, 766, 767, 768,
-                769, 770
+                769, 770, 771
             };
 
             if (Array.IndexOf(suppoertedVersionsProtocol18, protocolVersion) > -1)
@@ -360,6 +360,8 @@ namespace MinecraftClient.Protocol
                         return 769;
                     case "1.21.5":
                         return 770;
+                    case "1.21.6":
+                        return 771;
                     default:
                         return 0;
                 }
@@ -444,6 +446,7 @@ namespace MinecraftClient.Protocol
                 768 => "1.21.2",
                 769 => "1.21.4",
                 770 => "1.21.5",
+                771 => "1.21.6",
                 _ => "0.0"
             };
         }