Take an incremental backup: copy only the pages of each heap/idx file whose
page LSN is greater than base.source_lsn, plus any non-paged file (e.g.
catalog.bin) that changed. Builds on base (a full backup or a prior
increment’s effective state).
Rebuild a data dir from a full base backup plus an ordered chain of
increments. Verifies chain continuity (each increment’s base_source_lsn
must equal the running high-water LSN) and blake3-checks every file/delta,
then validates the result by reopening the catalog.