Add optional per-job pacing bounds across the cron API, CLI, tool schema, public output, and SQLite job envelope, requiring at least one bound. Allow only the currently running paced job to record a one-shot next_check proposal and carry it through isolated-run completion.
After successful runs, clamp the proposal to the job bounds and persist an exact one-shot slot marker so maintenance preserves only that timestamp. Clear the marker on runs, edits, and schedule normalization; preserve existing no-proposal, skip, timeout, and error scheduling behavior.
