Fixes #4848. Set Console.OutputEncoding to UTF-8 in AnsiOutput

Terminal.Gui/Drivers/AnsiDriver/AnsiOutput.cs

@@ -58,6 +58,13 @@ public AnsiOutput ()
 
         try
         {
+            // Ensure the console output code page is UTF-8 (65001). The ANSI driver writes
+            // UTF-8 encoded bytes via WriteFile; without this, a fresh Windows terminal uses
+            // its default OEM code page (e.g. 437), causing multi-byte UTF-8 characters
+            // (box-drawing glyphs, etc.) to be misinterpreted as garbled single-byte characters.
+            // See https://github.com/gui-cs/Terminal.Gui/issues/4848
+            Console.OutputEncoding = Encoding.UTF8;
+
             // Check if we have a real console first
             if (!IsAttachedToTerminal)
             {