Codex gate (CORE, reproduced): _reload_dotenv() copies a profile's .env into os.environ, so a
contained user could set HERMES_WEBUI_ISOLATED_PROFILE=0 in their own profile .env and silently
escape isolation. Fix: _PROTECTED_ENV_KEYS — _reload_dotenv refuses to override operator/deployment
keys from a profile .env (logs a warning). + regression test proving .env can't disable isolation.