The reviewed maintenance plan gains workflow_storage. Applying it starts
"Store each workflow once": kind maintenance, records admission,
cancellable, groups changed/protected/errors.
- The promised verified safety backup comes first; a failed backup ends the
job with nothing rewritten. The apply's up-front disk check covers it.
- Old-form rows are rewritten batch by batch on the event loop's executor,
with progress after each committed batch. Cancel stops between batches;
a failed batch rolls back whole and fails the job with a coded message.
Either way every record reads as before and the next apply continues.
- When every row was looked at, "Reclaim space" starts: exclusive (runs
alone), not cancellable. It checks the disk for VACUUM's copies of the
live pages, then sweeps, runs VACUUM and truncates the WAL. If another job
holds the registry it does not start, and the finished migration says so
and names Optimize database.
- No image or video file is opened; tests track every open under the
output folder and compare the media bytes and mtimes.