Implemented the next 4h-plan phase: dual-run support + explicit cutover gate.

scripts/rainml_py.sh

@@ -16,12 +16,16 @@ Examples:
 Optional:
   RAINML_PY_BUILD=1 scripts/rainml_py.sh ...
   (builds the rainml image before running)
+  RAINML_PY_SERVICE=rainml_1h scripts/rainml_py.sh ...
+  (runs against a specific compose service; default is rainml)
 EOF
   exit 1
 fi
 
+SERVICE="${RAINML_PY_SERVICE:-rainml}"
+
 if [[ "${RAINML_PY_BUILD:-0}" == "1" ]]; then
-  docker compose build rainml
+  docker compose build "$SERVICE"
 fi
 
-docker compose run --rm --no-deps --entrypoint python3 rainml "$@"
+docker compose run --rm --no-deps --entrypoint python3 "$SERVICE" "$@"