Make lerna exec suitable for reproducible automation by adding explicit environment overlays for commands…

Make lerna exec suitable for reproducible automation by adding explicit environment overlays for commands…: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). Add repeatable --env-file <path and --package-env-file <path options, plus repeatable inline --env KEY=VALUE…