Capture the command output in the parent-directory export test

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tools/tests/test_export_llm_input.py

@@ -189,6 +189,8 @@ class TestExportLlmInput(unittest.TestCase):
         created when missing."""
         self.__seed([("Hello", "Adele", "hello lyrics\n")])
         nested: Path = self.__dir / "nested" / "dir" / "out.jsonl"
+        stderr: io.StringIO = io.StringIO()
+        with redirect_stderr(stderr):
             status: int = export_llm_input.main([str(nested)])
         self.assertEqual(status, 0)
         self.assertTrue(nested.exists())