Fix load harness cleanup exit code and record passing smoke evidence

tests/load/collaboration/run_load.sh

@@ -43,7 +43,10 @@ cleanup() {
     "$ROOT/scripts/svc.sh" u7load stop >/dev/null 2>&1 || true
     "$ROOT/scripts/svc.sh" rm u7load --purge >/dev/null 2>&1 || true
   fi
-  [[ $KEEP -eq 1 ]] && echo "[load] --keep：栈保留（PG=u7load:$PG_PORT，app=127.0.0.1:$APP_PORT，结果 $RESULTS）"
+  if [[ $KEEP -eq 1 ]]; then
+    echo "[load] --keep：栈保留（PG=u7load:$PG_PORT，app=127.0.0.1:$APP_PORT，结果 $RESULTS）"
+  fi
+  return 0 2>/dev/null || true
 }
 trap cleanup EXIT