test(controller): cover reconcileInstanceGates replica counting and gate clearing

Adds unit coverage for the WorkloadDeployment controller's replica
bucketing (updated/current/ready/quota-blocked), the network
scheduling-gate clearing path, the nil Spec.Controller and nil
Status.Controller regressions, and the finalizer-add requeue with
status publication (ObservedGeneration, DesiredReplicas, ReplicasReady).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: scotwells