Fix #5: clarify parent directory icon

tests/test_import_export_workflow.py

@@ -3,6 +3,7 @@
 from unittest.mock import Mock
 
 import pytest
+from rich.style import Style
 from textual.containers import Vertical
 from textual.widgets import Button, DirectoryTree, Input, RadioButton, RadioSet, Static
 
@@ -141,6 +142,9 @@ async def test_file_browser_presents_parent_directory_as_dot_dot(tmp_path):
         await pilot.pause()
 
         assert str(tree.root.children[0].label) == ".."
+        assert tree.render_label(
+            tree.root.children[0], Style(), Style()
+        ).plain.startswith("↑ ")
         assert len(browser.query("#up-button")) == 0
 
         tree.focus()