Add chat.max_announcement_length cvar (#23571)

* Add announce message length to UI and make a cvar for it

* Update comm console server-side trim to use the cvar

* Rely on the new OnTextChanged event

Because OnKeyBindUp only works for keys that have binds

* Add a similar indicator to nukies' war declaration UI

* Remove message length indicators for now cuz it requires the engine update

* Rename cvar slightly

* Refactor duplicated code to a helper method

* Remove message trimming from *Window class as it's better to live in the BoundUserInterface where the other message handling happens

* Rename to chat.max_announcement_length

Content.Shared/Chat/SharedChatSystem.cs

@@ -184,4 +184,34 @@ public abstract class SharedChatSystem : EntitySystem
 
         return message;
     }
+
+    public static string SanitizeAnnouncement(string message, int maxLength = 0, int maxNewlines = 2)
+    {
+        var trimmed = message.Trim();
+        if (maxLength > 0 && trimmed.Length > maxLength)
+        {
+            trimmed = $"{message[..maxLength]}...";
+        }
+
+        // No more than max newlines, other replaced to spaces
+        if (maxNewlines > 0)
+        {
+            var chars = trimmed.ToCharArray();
+            var newlines = 0;
+            for (var i = 0; i < chars.Length; i++)
+            {
+                if (chars[i] != '\n')
+                    continue;
+
+                if (newlines >= maxNewlines)
+                    chars[i] = ' ';
+
+                newlines++;
+            }
+
+            return new string(chars);
+        }
+
+        return trimmed;
+    }
 }