Function run_disk_writer 

pub async fn run_disk_writer(log: Arc<EventLog>, events_rx: Receiver<Event>)

Background task: write events to the disk file as they arrive on the broadcast bus. Rotates when the file exceeds MAX_DISK_BYTES.

Spawned once per launcher run from main.rs. Holds a tokio broadcast receiver and the EventLog’s disk path. Failures log a warning and drop the event from the disk stream (in-memory ring is unaffected — disk is forensics-only).