🚸 Improve checks for offline cache directory specification

[kzscisoft]

Fix failing cache directory

Issue: #848

Python Version(s) Tested: 3.13

Operating System(s): Ubuntu 25.04

📝 Summary

offline.cache key fails validation on Windows systems due to constraints.

🔍 Diagnosis

Windows CI fails due to ~ in path.

🔄 Changes

Checks were updated to:

• Confirm location's parent directory exists.
• Confirm the parent directory is writable.

✔️ Checklist

• Unit and integration tests passing.
• Pre-commit hooks passing.
• Quality checks passing.