A hand-edited "completed": "2" still crashed every recorded run ("2" + 1),
and 1.0 was stored as 2.0 ("2.0/3"). load_jobs now coerces any non-int
counter to a non-negative int (0 when unparseable). Document the load-time
repair next to the direct-edit tip.
Co-authored-by: John Paul Soliva <soliva.johnpaul@icloud.com>