Make the template-file utilities safe to use as the generator's filesystem boundary.

Make the template-file utilities safe to use as the generator's filesystem boundary.: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). Keep the existing parameter lists of TemplateFileAndOverwrite and TemplateFileIfDoesNotExist, but have each return a receive-only…