GKE Gateway API: Full Setup & Troubleshooting Runbook

I recently went through the full process of setting up GKE Gateway API on a production-grade cluster — Fleet registration, controller enablement, Helm deployment, and a handful of painful debugging sessions. This is the cleaned-up runbook so you don't have to learn these lessons the hard way. Cluster Context Field Value Project my-gcp-project Cluster my-gke-cluster Region us-east1 Namespace my-namespace Traffic flow: Client → Cloud Load Balancer → GKE Gateway (L7) → HTTPRoute → Kubernetes Servic