getsentry/cli uses setEnv/getEnv for env isolation in tests

The repo isolates environment variables via src/lib/env.ts — setEnv(env) overrides the active env, getEnv() returns it. Tests that depend on env vars should call setEnv({ VAR: 'val' } as NodeJS.ProcessEnv) and restore with setEnv(process.env) in a try/finally. Detection functions like detectAgent() read from getEnv(), not process.env directly.