pm-triage-listen.ts: realtime watermark can permanently skip rows during outage window

Watermark advances on delivered realtime notifications independent of whether catch-up ran. A submit landing in a dead window during an outage/downtime ends up below the watermark permanently — catch-up can never re-emit it. Silent loss, not delayed delivery. Found by coder-pluto-cc while landing pluto's slot (8449480); pluto got lucky (6 rows since 07-03, all already resolved by other means). Structural gap in the shared script — affects both venus and pluto units. Not urgent, no current data loss.