test(multiplayer): cover cooldown response boundary

server/store/proposal_recovery_sql.go

@@ -116,15 +116,10 @@ SET state = 'DECLINED', revision = revision + 1
 WHERE proposal_id = $1 AND state = 'OPEN'`
 
 // ProposalDeclineRequeueSQL requeues every participant's ticket, including
-// the decliner's own: nothing yet enforces the decline cooldown §8.17
-// documents as a separate, not-yet-built feature, so leaving any ticket
-// behind at PROPOSED here isn't "cooldown behaviour", it's just a stranded
-// ticket -- invisible to the matcher (which only ever reads state='QUEUED'),
-// still counted as this player's one active ticket (blocking a fresh
-// queue_create), and renewable forever by an ordinary heartbeat, so a player
-// left in this state has no path back into matchmaking without realising
-// they need to cancel and start over. Once §8.17's cooldown exists, it can
-// exempt the decliner from this immediate requeue; today nothing does.
+// the decliner's own. The durable decline penalty separately prevents that
+// player from immediately creating a replacement ticket; leaving this ticket
+// at PROPOSED would not implement a cooldown, it would strand the player and
+// hide the ticket from the matcher.
 const ProposalDeclineRequeueSQL = `UPDATE queue_tickets q
 SET state = 'QUEUED', expires_at = $2, revision = revision + 1
 FROM proposal_participants pp