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>

docs/kvm-provider.md

@@ -264,6 +264,14 @@ The provider logs through controller-runtime's logger, named `kvm`, with
   cleaned when the same Proxy reconciles again (Delete removes volumes by
   name even with no domain), but a Proxy CR that is gone for good leaves
   them for `virsh vol-list` to find.
+- **A host removed from the config takes its VMs with it.** `Delete` for a
+  providerID naming an unconfigured host is a no-op success, so the Proxy
+  finishes deleting instead of pinning its finalizer, but the domain and its
+  volumes stay on the hypervisor and orphan GC cannot see them either (it
+  only sweeps configured hosts). Delete the Proxies before retiring a host,
+  or clean up afterwards with `virsh undefine --nvram` plus `virsh vol-delete`.
+  `Get` still fails permanently for such a providerID on purpose: a typo in
+  `hosts` must not look like a missing VM and trigger a rebuild elsewhere.
 - **The first image fetch is synchronous.** It holds a reconcile worker
   for the download (LAN speed, a few hundred MB, once per image per
   host). Other Proxies keep reconciling on the remaining workers.