Fix panic when global config dir does not exist yet

[fnando]

What

Do not crash when global dir cannot be expanded.

Why

Having a local config directory and no global directory was failing, even for commands that are read-only.

Known limitations

N/A

[Copilot]

Pull request overview

Prevents print_deprecation_warning from panicking when the computed global config directory path doesn’t exist yet (e.g., first-run scenarios), improving CLI robustness for read-only commands that still trigger the local-config deprecation warning.

Changes:

• Replace fs::canonicalize(...).expect(...) with a non-panicking fallback when canonicalization fails.
• Add a regression test to ensure print_deprecation_warning doesn’t panic when the global config dir is missing.