A backup under --skip-errors printed its skip errors and failed count,
then "Finished successfully.", and exited 0, so a cron wrapper could
not tell it from a complete backup. A directory the walk could not list
was not counted at all.
Each entry the walk skips is now counted as examined and failed. When
--skip-errors skipped anything it could not read or list, the run keeps
its snapshots, runs the post-backup prune as before, and then returns
an error the command reports as "Backup completed, but N file(s) could
not be read". A file removed during the run is still counted as failed
in the summary but leaves the exit status at 0, with or without the
flag.
Model: opus-5-5
