Piscina worker threads outlive process.exit() and linger as orphaned
processes holding DB connections/locks after a deploy restart. Two live
gateways then fight over the same messages table rows (one claims
processing, the other reverts), which left messages stuck in
ai_status='processing' forever.
Destroy both worker pools before closing the DB, with a 5s fallback so
a hung vision job cannot block shutdown indefinitely.
asepharyana
deed7bdfb0