Pause or resume schedule

Pause or resume a published pipeline's schedule. Pausing flips the flag the cron runner checks without touching the published graph, so the deployed snapshot stays an honest record of what was published. Resuming re-anchors the schedule to now, so it waits for the next real slot instead of replaying slots missed while paused. Requires the pipelines:write scope. Schedules themselves are authored as a schedule-trigger node (see get_node_type) and armed by publish_pipeline.