feat: toggle hidden directories in cd-browser with . key

tests/test_cli.py

@@ -4,9 +4,10 @@ import pytest
 
 from app.cli import run_cli
 from app.navigator import Navigator
+from app.ui import TerminalUI
 
 
-class StubUI:
+class StubUI(TerminalUI):
     def __init__(self, result: Path) -> None:
         self.result = result
         self.navigator: Navigator | None = None