- Added rich error reporting to install_repos() for clearer installer failure context
(repository identifier, repo directory, installer name, exit code).
- Updated E2E test 'install_all_shallow' to show additional diagnostics,
including Nix profile dumps and contextual SystemExit handling.
- Removed outdated/deactivated test file.
- New test now mirrors the robust debugging flow of the pkgmgr-only test.
See conversation for full context:
https://chatgpt.com/share/6936241b-52ec-800f-9859-1734a581c002
