Scope is a runtime concern, not a checkbox

Most pen-test platforms treat scope as a setup-time policy. We treat it as a runtime concern, enforced at three layers:

1. policy_check(action, context, scopes, rate_limiter) in the agent loop.
2. An HTTP forward-proxy (scope-proxy) that drops out-of-scope traffic at the network layer with a 451.
3. An append-only audit log of every blocked attempt for incident response.

Defense in depth: even if an agent imports its own httpx and forgets the policy check, the proxy still drops the request.