Add chat formatting code propagation (bold, italic, underline, strikethrough, obfuscated)

Re-implements PR #2851 against the current System.Text.Json.Nodes codebase.

Changes:
- ChatParser.cs: Add FormattingCodes dict, update JSONData2String to propagate
  formatting codes alongside colors, update NbtToString for the NBT chat path
  (used in MC 1.20.4+), fix root-string shortcut to preserve formatting prefix
- DiscordBridge.cs: Add GetDiscordText() converting § codes to Discord Markdown,
  handle unclosed formatting codes with end-of-string matching

End-to-end tested against Minecraft 1.21.11 (MC 26.1) offline server.
All 8 formatting types verified: bold(§l), italic(§o), strikethrough(§m),
underline(§n), combined, nested, reset-via-false, obfuscated(§k).

Co-authored-by: milutinke <441903+milutinke@users.noreply.github.com>
Agent-Logs-Url: https://github.com/MCCTeam/Minecraft-Console-Client/sessions/65b0d230-287c-4ed8-9b3c-a5ea25411804

MinecraftClient/ChatBots/DiscordBridge.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 using Brigadier.NET.Builder;
 using DSharpPlus;
@@ -222,7 +223,22 @@ namespace MinecraftClient.ChatBots
                 SendMessage(messageBuilder);
                 return;
             }
-            else SendMessage(message);
+            else SendMessage(GetDiscordText(message));
+        }
+
+        /// <summary>
+        /// Converts Minecraft § formatting codes to Discord Markdown equivalents
+        /// and strips remaining § codes.
+        /// Handles both properly closed formatting (§l...§r) and unclosed formatting (§l... end).
+        /// </summary>
+        private static string GetDiscordText(string text)
+        {
+            text = Regex.Replace(text, @"§l(.*?)(?:§r|$)", "**$1**");
+            text = Regex.Replace(text, @"§m(.*?)(?:§r|$)", "~~$1~~");
+            text = Regex.Replace(text, @"§n(.*?)(?:§r|$)", "__$1__");
+            text = Regex.Replace(text, @"§o(.*?)(?:§r|$)", "*$1*");
+            text = Regex.Replace(text, @"§.", "");
+            return text;
         }
 
         public void SendMessage(string message)