Step 1 of 2 to hand the coredns ConfigMap back to Talos. It is a Talos
bootstrap manifest (talos-bootstrap-manifests-inventory) that Flux also
applies; talosctl upgrade-k8s reverts Flux's Corefile. Bootstrap already
runs on Talos's Corefile (forward to the node resolver, which asks
k8s-gateway first), and k8s-gateway carries serve_stale for every name,
so the Flux copy is redundant.
With prune disabled, step 2 can drop the file without Flux deleting the
live ConfigMap.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>