The old script grouped backups with cut -d'-' -f1-3, which mis-grouped
volume keys and permanently deleted ~360 archives on 2026-06-11. Replace
with safe retention: group by full volume key regex, keep 3 newest per key,
move excess to /backup/trash, and protect uploading-*, broken_*, and
deprecated-* prefixes.
Co-authored-by: Cursor <cursoragent@cursor.com>