Adds _normalize_path() helper that calls expanduser().resolve() to
properly handle tilde paths (e.g. ~/.hermes, ~/.config). Previously
Path.resolve() alone treated ~ as a literal directory name, producing
invalid paths like /root/~/.hermes.
Also improves _run_git() error handling to distinguish missing working
directories from missing git executable, and adds pre-flight directory
validation.
Cherry-picked from PR #7898 by faishal882.
Fixes#7807
90352b2adf