build: rename repository folder ChatTwo to HellionChat

Repository folder, csproj, solution and all CI/build paths now use
the consolidated HellionChat name.

- ChatTwo/ → HellionChat/ (git mv preserves history with --follow)
- ChatTwo.csproj → HellionChat.csproj
- ChatTwo.sln → HellionChat.sln; obsolete Tests project entry removed
  (private/untracked sandbox)
- AssemblyInfo.cs InternalsVisibleTo for ChatTwo.Tests removed
  (file emptied; can be repopulated when actual tests land)
- repo.json and yaml image URLs updated (ChatTwo/images/ → HellionChat/images/)
- .github/workflows/{build,codeql,release}.yml csproj paths
- .github/dependabot.yml directory path

Functional behavior unchanged.

HellionChat/GameFunctions/ChatBox.cs

@@ -0,0 +1,43 @@
+using System.Text;
+using HellionChat.Resources;
+using Dalamud.Memory;
+using FFXIVClientStructs.FFXIV.Client.System.String;
+using FFXIVClientStructs.FFXIV.Client.UI;
+
+namespace HellionChat.GameFunctions;
+
+public unsafe class ChatBox
+{
+    public static void SendMessageUnsafe(byte[] message)
+    {
+        var mes = Utf8String.FromSequence(message.NullTerminate());
+        UIModule.Instance()->ProcessChatBoxEntry(mes);
+        mes->Dtor(true);
+    }
+
+    public static void SendMessage(string message)
+    {
+        var bytes = Encoding.UTF8.GetBytes(message);
+        if (bytes.Length == 0)
+            throw new ArgumentException(Language.ChatBox_Error_Empty, nameof(message));
+
+        if (bytes.Length > 500)
+            throw new ArgumentException(Language.ChatBox_Error_Too_Long, nameof(message));
+
+        if (message.Length != SanitiseText(message).Length)
+            throw new ArgumentException(Language.ChatBox_Error_Invalid, nameof(message));
+
+        SendMessageUnsafe(bytes);
+    }
+
+    private static string SanitiseText(string text)
+    {
+        var uText = Utf8String.FromString(text);
+
+        uText->SanitizeString((AllowedEntities) 0x27F);
+        var sanitised = uText->ToString();
+        uText->Dtor(true);
+
+        return sanitised;
+    }
+}