Bounded waits do not cancel background attribution writes

When a voice pipeline persists selected and constructed attribution using synchronous database clients inside asyncio.to_thread, timing out the await does not stop the database write. A late preliminary write can overwrite newer constructed evidence. Avoid redundant preliminary writes on the baseline path; for required preliminary writes, abort before construction on timeout, or enforce monotonic stages in the database. This preserves bounded startup without pretending background work was cancelled. The appropriate policy depends on whether missing attribution must stop admission; it does not prove media delivery. Applies when: sequential state updates use background synchronous I/O with bounded async waits. Keywords: Python asyncio timeout thread database attribution canary voice state