Clarify which criterias must be met for a backup rollback will be initiated

### Checklist

- [X] I have verified this is the correct repository for opening this issue.
- [X] I have verified no other issues exist related to my request.

### Is Your Feature Request Related To A Problem? Please describe.

There are some uncertainty of when a backup will be restored, or a package will be rolled back in case of upgrade and uninstall failures (or a forced installation).

### Describe The Solution. Why is it needed?

We need to investigate when a rollback is being asked of the user, when a rollback will be automatically initiated, and when no rollback will occur.

Most likely, there is just a need to document the rollback behavior, but code changes may be needed if we find situations where it does not behave as expected.

### Additional Context

_No response_

### Related Issues

_No response_

The issue names no file, test, or entry point. Start by tracing the documented and implemented rollback paths for backup restoration, upgrade and uninstall failures, and forced installs; define when rollback is user-requested, automatic, or skipped, then record the verified behavior and any gaps.

Written by the indexing model from the issue text.