test(cli): gate only the POSIX mode-bit assertion on Windows

[LceAn]

What & why

Native Windows does not expose POSIX permission bits from os.chmod(..., 0o600), so the credential-shaped restore test failed on st_mode even though restoration was correct.

Change

Keep the test enabled on every platform and gate only the POSIX-specific 0o600 assertion. Windows still verifies the restored home-relative path, file contents, and absence of _external leakage under HERMES_HOME.

Validation

• The focused external-restore test passes on native Windows.
• ruff and git diff --check pass.

This follows the reviewer-requested assertion-level scope and the repository precedent in #60888.

[teknium1]

Thanks for the focused Windows portability fix. The premise remains valid on current main: tests/hermes_cli/test_backup.py:2471 unconditionally checks 0o600, while hermes_cli/backup.py:599-604 writes the external file and applies os.chmod.

Problems

• The added method-level marker skips more than the POSIX-specific assertion. It also removes Windows coverage for the portable restore assertions at tests/hermes_cli/test_backup.py:2467-2473: file existence, restored content, and preventing _external from appearing under HERMES_HOME.

Suggested changes

• Keep the test running and guard only the mode-bit assertion at tests/hermes_cli/test_backup.py:2471 on Windows. This follows the linked #60888 discussion's stronger pattern of retaining meaningful Windows behavior coverage while excluding unsupported POSIX mode checks.

Automated hermes-sweeper review.

[teknium1]

Skipping the entire method also drops Windows coverage of the portable restoration assertions below: file existence, contents, and no _external leak into HERMES_HOME. Keep the test enabled and condition only the POSIX-mode assertion.

[LceAn]

Updated per review. The test now stays enabled on Windows and only the 0o600 assertion is gated with if os.name != "nt"; existence, content, and no-_external-leak coverage still runs there.

Validation: scripts/run_tests.sh tests/hermes_cli/test_backup.py -q -k test_import_restores_external_to_home_relative_location → 1 passed.

[LceAn]

Maintenance update: rebuilt the same reviewed assertion-level fix on current main because this large test file changed upstream, then normalized it to LF and refreshed the title/body. Windows still runs the portable restore assertions; only the POSIX mode-bit check is gated. The diff is now +3/-2.

[LceAn]

Second-pass maintenance: retained the reviewer-approved assertion-level gate after revalidation. Windows continues to cover restore path, content, and _external isolation; only POSIX mode bits are excluded.