New hermes_cli/managed_scope.py resolves a system-level managed directory
(HERMES_MANAGED_DIR override > /etc/hermes), parses managed config.yaml/.env
with fail-open semantics, and exposes is_key_managed/is_env_managed helpers.
The system default is ignored under pytest and HERMES_MANAGED_DIR is added to
the conftest env scrub so a real managed scope can't leak into the suite.
Not wired into the load paths yet (Phases 2-3).
