## What changed
- Add `EnvironmentNetworkPolicy` as a serializable view of portable domain,
Unix-socket, upstream-proxy, and local-binding restrictions without exposing
controller-owned proxy runtime settings.
- Add an optional `network_policy` field to `EnvironmentConfig` and re-export
the policy and related permission types through the core APIs.
- Reject owner-provided network policies during environment preview and
readiness until runtime enforcement is implemented, while preserving the
existing controller policy when the field is absent.
## Testing
- Cover rejection through both environment preview and readiness, including
preservation of the existing environment selection.
GitOrigin-RevId: 80ad4cf4d4a45632daa7a823e6cf568eb0e8bb80