Add an egress policy module (`security.egress_policy`) that gates search-engine instantiation against a user-declared scope. New settings `policy.egress_scope` (default `both`, preserves current behavior), `llm.require_local_endpoint`, `embeddings.require_local`, and `llm.allowed_local_hostnames` are reserved. Under `strict` scope the factory blocks any engine that isn't the user's primary, closing the previously silent expansion path. The LangGraph agent tool-list filter, LLM/embeddings PEPs, and UI controls ship in the same release (see the related Stage 1b changelog entries).
