Only message-linked traces cascaded, so scheduled runs, stateless /v1
rounds and unreserved turns kept their previews after the conversation was
deleted; they are now deleted by conversation_id. The Logs search and graph
branches filter by source, so the listing indexes lead with it.
One row per execution holding its span tree as JSONB, linked to Logs rows
by request, message, activity and workflow-run ids. message_id cascades so
deleting or truncating a conversation drops its traces; a daily beat task
enforces TRACES_RETENTION_DAYS.
arc53-machine