test: add test for Unicode to ASCII fallback in tool messages

tests/basic/test_io.py

@@ -285,6 +285,25 @@ class TestInputOutputMultilineMode(unittest.TestCase):
         self.io.toggle_multiline_mode()
         self.assertFalse(self.io.multiline_mode)
 
+    def test_tool_message_unicode_fallback(self):
+        """Test that Unicode messages are properly converted to ASCII with replacement"""
+        io = InputOutput(pretty=False, fancy_input=False)
+        
+        # Create a message with Unicode characters
+        unicode_message = "Hello こんにちは Привет"
+        
+        # Mock console.print to capture the output
+        with patch.object(io.console, 'print') as mock_print:
+            io._tool_message(unicode_message)
+            
+            # Verify that the message was converted to ASCII with replacement
+            mock_print.assert_called_once()
+            args, kwargs = mock_print.call_args
+            converted_message = args[0]
+            
+            # The Unicode characters should be replaced with '?'
+            self.assertEqual(converted_message, "Hello ????? ?????")
+
 
 if __name__ == "__main__":
     unittest.main()