Constant SWEEP_INTERVAL 

const SWEEP_INTERVAL: Duration;

Same cadence class as FsWatchPool::HEALTH_SWEEP_INTERVAL (backend/fs_watch/recovery.rs) — chosen for the same reason: frequent enough that an operator reviewing history isn’t waiting long for a drifted write to surface, infrequent enough not to matter for a background sweep over what’s normally a handful of small markdown files per agent.