test: make release report path assertion portable on Windows

Summary

frontends/tests/test_release_qualification.py compares a native path to the literal POSIX suffix bootstrap/first-launch. On Windows, GA_DESKTOP_E2E_REPORT_DIR contains backslashes, so the release-qualification test fails even though the application provides the expected directory.

Reproduction

On Windows with Python 3.13:

python -m pytest frontends/tests/test_release_qualification.py

The first-launch application test fails at the .endswith("bootstrap/first-launch") assertion. The captured value ends with reports\bootstrap\first-launch.

Expected behavior

The test should compare path components (for example with pathlib.Path) so it passes for both POSIX and Windows separators.

Scope

This is limited to the test assertion; the production code already supplies the correct report directory. I did not find an existing issue or PR covering this path-separator failure.