Hot lean rows, sealed compressed archive, queue on low disk

The storage tiers that answer UD-S5: the HOT store is the lean layout (lean-v1), keeping every chain hash; the ARCHIVE is compressed, sealed columnar segments with a chain checkpoint every 64 rows, released only after an unseal proof; when disk runs low, new runs QUEUE and nothing is deleted (UD-S3). The archive tier itself is SCALE-9’s.