Prime's ruling 2026-10-02. retention.py picks the snapshots to delete:
the newest 48, plus the newest of each of the last 30 days and of each of
the last 12 ISO weeks, counting only days and weeks that have snapshots.
Names that are not exactly YYYY-MM-DD_HHMM are never selected, and the
NAS side refuses any path outside that pattern. The unit fails unless
the number kept equals the number expected. Live run: deleted 1, 0
errors, 48 kept as expected.
