Let a Proxy finish deleting when its instance can no longer be reached

reconcileDelete asked Get first and dropped the finalizer only on
not-found, so a permanent Get retried forever: a KVM host removed from
the config, or a providerID the provider cannot resolve, left the Proxy
in Terminating with no way out. It now tries Delete anyway, which is
idempotent and can still finish where Get cannot converge, and releases
the object when that succeeds.

crawl.example.com/skip-cleanup abandons the instance for the cases that
stay stuck, such as revoked credentials. It is checked before the
provider lookup, so it also frees a Proxy whose provider is gone from
the config.

In the KVM provider, Delete over an unconfigured host is now a no-op
success, mirroring removeVolumes over a missing pool. Get keeps failing
permanently there on purpose: the live path reads not-found as "rebuild
it", so a typo in hosts must not look like a missing VM.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

internal/provider/kvm/kvm.go

@@ -451,7 +451,8 @@ func mapState(s libvirt.DomainState, ip string) provider.InstanceState {
 // domain is not destroyed again, a missing domain is not undefined, and
 // the per-VM volumes are removed by name even when the domain is already
 // gone, so a crash between volume creation and define is cleaned up on the
-// next reconcile.
+// next reconcile. A providerID naming a host that is no longer configured
+// is a no-op success rather than an error.
 func (p *Provider) Delete(ctx context.Context, providerID string) error {
 	hostName, name, err := parseProviderID(providerID)
 	if err != nil {
@@ -459,7 +460,14 @@ func (p *Provider) Delete(ctx context.Context, providerID string) error {
 	}
 	host, err := p.host(hostName)
 	if err != nil {
-		return p.wrapErr("delete", providerID, err)
+		// The host is no longer configured, so this operator has no way to
+		// reach the domain and nothing left to clean. Same reasoning as
+		// removeVolumes over a missing pool: refusing would pin the Proxy's
+		// finalizer. Whatever is still running there is the admin's to remove,
+		// and orphan GC cannot see it either — see docs/kvm-provider.md.
+		p.logger(ctx).Info("host is not configured; delete has nothing to clean up",
+			"host", hostName, "providerID", providerID)
+		return nil
 	}
 	log := p.logger(ctx).WithValues("host", host.Name, "name", name)
 	err = p.hosts.call(ctx, log, host, func(api libvirtAPI) error {