Remove the kubeconfig port forwarding feature and update the doctor
llm-help prompt and debug-navigator-cluster skill to reflect the
current deployment state: openshell namespace, openshell-* resource
names, correct mTLS credential paths, and new failure patterns.
* refactor(docker): rename server image to gateway
Rename Dockerfile.server to Dockerfile.gateway and update all image
references from openshell/server to openshell/gateway across Helm
charts, Kubernetes manifests, mise tasks, build/deploy scripts, CI
workflows, and documentation.
The underlying Rust binary (navigator-server) is unchanged -- this
rename only affects the Docker image name and Dockerfile.
* fix: catch remaining server->gateway references in docs and comments
Drew Newberry