Save Backup System

Save files should follow the correct logic to write and overwrite a file while preserving at least one back up.

1. The save file should be written to a temporary file (.new).
2. The backup save file should be renamed to a name that indicates it'll be erased (.old).
3. The current save file should be renamed to the backup save file name (.bak).
4. The new save file should be renamed to the current name.
5. The save file marked for deletion should be erased (.old).

Any failure on this process should roll back all changes by executing the logic in reverse.

The issue names no files, tests, or entry points. Start by locating the save-file write and overwrite logic, then trace how failures are handled. Done means writes use the .new, .old, and .bak sequence, preserve one backup, and reverse all completed changes when any step fails.