描述
Organize application environment configuration: `.env` files, env precedence, typed env validation, secret handoff, framework-specific env rules, and config drift between local, staging, CI, and production. Use when the user needs help structuring environment variables, validating required config, separating public/private env values, or cleaning up env-file sprawl. This is the narrower app-config compatibility skill. Route broader runnable-machine, Docker, devcontainer, onboarding, and local-service setup work to `system-environment-setup`.