🐛 FIX: Support rooted tar members

[Mirochill]

Summary

• Normalize rooted tar member names so TarPath exposes them as relative archive paths.
• Resolve rooted members when checking existence, reading files, iterating, globbing, and extracting.
• Add a regression covering a tar member stored as /bin/garbage.txt.

Validation

• Not run locally.
• git diff --check
• git diff --cached --check
• git show --check --stat --oneline HEAD -- archive_path/tar_path.py tests/test_basic.py

Closes #17