fix: Support hex RGB colors (#RRGGBB) in chat messages (fixes #2054)

Minecraft 1.16+ servers can send custom hex colors in JSON text
components ("color": "#RRGGBB"). MCC's ChatParser.Color2tag() only
recognized the 16 named colors, silently dropping hex values and
leaving gradient/custom-colored chat as uncolored plain text.

- ChatParser: recognize hex color values and emit internal §#rrggbb
  encoding; extend ColorCodeRegex to match the new format
- ClassicConsoleBackend: resolve §#rrggbb to ANSI escape codes via
  ColorHelper before passing to ConsoleInteractive (adapts to the
  configured ConsoleColorMode: 24-bit, 8-bit, 4-bit, or disable)
- McColorParser (TUI): parse §#rrggbb into exact SolidColorBrush
  for full RGB fidelity in Avalonia
- ChatBot.GetVerbatim(): skip the full 8-char §#rrggbb sequence
  instead of only 2 chars, preventing hex digits from leaking into
  stripped text

Made-with: Cursor

MinecraftClient/Protocol/Message/ChatParser.cs

@@ -200,7 +200,12 @@ namespace MinecraftClient.Protocol.Message
         /// <returns>Color code</returns>
         private static string Color2tag(string colorname)
         {
-            return colorname.ToLower() switch
+            string lower = colorname.ToLower();
+
+            if (lower.Length == 7 && lower[0] == '#' && IsHexColor(lower))
+                return "§" + lower;
+
+            return lower switch
             {
 #pragma warning disable format // @formatter:off
 
@@ -227,6 +232,17 @@ namespace MinecraftClient.Protocol.Message
             };
         }
 
+        private static bool IsHexColor(string s)
+        {
+            for (int i = 1; i < s.Length; i++)
+            {
+                char c = s[i];
+                if (!((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f')))
+                    return false;
+            }
+            return true;
+        }
+
         /// <summary>
         /// Specify whether translation rules have been loaded
         /// </summary>
@@ -443,8 +459,8 @@ namespace MinecraftClient.Protocol.Message
             { "italic",        "o" },
         };
 
-        /// <summary>Matches a single color code (§0–§9, §a–§f). Used to strip color when replacing.</summary>
-        private static readonly Regex ColorCodeRegex = new(@"§[0-9a-f]", RegexOptions.Compiled);
+        /// <summary>Matches a single color code (§0-§9, §a-§f) or a hex color (§#rrggbb). Used to strip color when replacing.</summary>
+        private static readonly Regex ColorCodeRegex = new(@"§(?:[0-9a-f]|#[0-9a-f]{6})", RegexOptions.Compiled);
 
         /// <summary>
         /// Use a JSON Object to build the corresponding string