test: assert percent comment renders unchanged

[martinjm97]

Summary

• strengthen the percent-comment regression test to compare the complete rendered option help line
• verify the literal % is preserved rather than merely checking an unaffected substring

Testing

• PYTHONPATH=src ../repo/.venv/bin/python -m pytest tests/test_integration.py::EdgeCaseTests::test_comment_with_percent -q (1 passed)
• full Python 3.14 suite (359 passed, 4 skipped)
• ruff check tests/test_integration.py
• git diff --check