DL-082
Writer fencing for session-log persistence is force-teardown of the old container (PRIMARY fence) plus a per-container-lifetime epoch token in the object key (sessions/<session_id>/<epoch>.jsonl, BELT): force-teardown removes the zombie writer in the normal case, and the epoch guarantees a zombie from a crashed lifetime a Runner could not confirm torn down can only clobber its OWN dead epoch segment, never erase another lifetime’s segment
Status: Superseded by DL-085 (Matt, 2026-07-31)