Remove tools/setup-gcp and point docs to ai-on-gke/substrate-gke #3390

Sub-task of #2304. This covers only deleting tools/setup-gcp and pointing users to its new home, ai-on-gke/substrate-gke tools/setup-gcp. It does not cover the wider provider-extensibility work discussed in #2304.

Status

substrate-gke has a copy of tools/setup-gcp (imported from f69f41d, now its own Go module). As of 2026-10-28 it matches main except for two small items, plus GKE config that is still only in core. These are tracked in ai-on-gke/substrate-gke#82. Do not delete until ai-on-gke/substrate-gke#82 is done. Until then, please send setup-gcp changes to substrate-gke as well, or mention them in that issue, so the copies stop drifting.

Cleanup

Remove

• tools/setup-gcp/ (code, dashboards/, README.md, cloud-sql.md)
• /setup-gcp entry in .gitignore
• Run go mod tidy / go mod vendor and regenerate _LICENSES/. GCP libraries likely used only by setup-gcp, e.g. cloud.google.com/go/container, monitoring, serviceusage, resourcemanager, google.golang.org/api/sqladmin, should drop out. Confirm, since storage/iam are still used by internal/objectstore*.
• Check CI/workflows and the Makefile for anything that builds or tests ./tools/setup-gcp/...

Repoint docs to substrate-gke

Replace go run ./tools/setup-gcp ... and relative links with links to substrate-gke, and say in one place that GKE provisioning lives there:

• README.md: GKE quickstart (bootstrap, "what create iam actually grants", Create Cluster warning, individual steps, Cloud SQL link, repo layout list)
• AGENTS.md (provisioning pointer, e2e setup instructions)
• docs/operator-install.md (create iam / create bucket / bootstrap, asset bucket, upgrading an existing install)
• docs/observability.md and docs/dev/best-practices/metrics.md (dashboards now live in substrate-gke; new metrics that need a dashboard panel go there)
• docs/postgres.md, docs/dev/cloud-sql-scaling-guide.md, cmd/ate-setup/differences.md (cloud-sql.md links)
• docs/egress-credential-injection.md, docs/dev/code-layout.md, cmd/kubectl-ate/README.md
• benchmarking/automation/README.md, benchmarking/automation/setup.sh
• Comments: hack/ate-dev-env.sh.example, hack/install-microvm-deps.sh, hack/microvm-assets/README.md, hack/teardown.sh, internal/installdefaults/installdefaults.go, cmd/ate-setup/internal/config/config.go
• docs/threat-model.md / docs/threats.json mitigations that cite setup-gcp

git grep -n setup-gcp -- ':!tools/setup-gcp' lists all of them.

Out of scope (tracked in #2304 / ai-on-gke/substrate-gke#82)

GKE-specific config used by ate-setup: manifests/ate-install/atenet-router-monitoring.yaml (GMP PodMonitoring), manifests/ate-install/cloudsql/, hack/teardown.sh, hack/microvm-assets/stage-to-gcs.sh, and the GCS path in hack/install-microvm-deps.sh.