Fixes #5453. Fix Windows VT input encoding for IME and non-ASCII characters (#5454)

* Fixes #5453. Fix Windows VT input encoding for IME and non-ASCII characters

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* Cleanup code

* Apply suggested changes related with review feedback

---------

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Author: BDisp

Terminal.Gui/Drivers/WindowsHelpers/WindowsVTInputHelper.cs

@@ -51,6 +51,9 @@ internal sealed class WindowsVTInputHelper : IDisposable
     [DllImport ("kernel32.dll")]
     private static extern uint GetConsoleCP ();
 
+    [DllImport ("kernel32.dll", SetLastError = true)]
+    private static extern bool SetConsoleCP (uint wCodePageID);
+
     #endregion
 
     private const int ERROR_NOT_FOUND = 1168;
@@ -68,6 +71,22 @@ internal sealed class WindowsVTInputHelper : IDisposable
     private uint _originalConsoleMode;
     private bool _disposed;
 
+    private const uint CP_UTF8 = 65001;
+
+    private readonly uint _originalConsoleCP;
+
+    public WindowsVTInputHelper ()
+    {
+        _originalConsoleCP = GetConsoleCP ();
+
+        if (_originalConsoleCP == CP_UTF8 || SetConsoleCP (CP_UTF8))
+        {
+            return;
+        }
+        int error = Marshal.GetLastWin32Error ();
+        Logging.Warning ($"{nameof (WindowsVTInputHelper)}: Failed to set console input code page to UTF-8. Win32 error: {error}");
+    }
+
     /// <summary>
     ///     Gets whether VTS input mode was successfully enabled.
     /// </summary>
@@ -238,6 +257,7 @@ public void Restore ()
 
         try
         {
+            SetConsoleCP (_originalConsoleCP);
             SetConsoleMode (InputHandle, _originalConsoleMode);
             IsEnabled = false;
         }