fix: add matrix notifications for silent failure paths

dev-poll.sh:
- Merge conflicts (rebase attempt + outcome)
- Non-conflict merge failures (HTTP code)
- Low memory skip
- New issue launch

review-poll.sh:
- Review script failure

review/review-poll.sh

@@ -78,6 +78,7 @@ while IFS= read -r line; do
     REVIEWED=$((REVIEWED + 1))
   else
     log "  #${PR_NUM} review failed"
+    matrix_send "review" "❌ PR #${PR_NUM} review failed" 2>/dev/null || true
   fi
 
   if [ "$REVIEWED" -ge "$MAX_REVIEWS" ]; then