proxmox: Delete with seed cleanup, health Checker, CRD type comment

Delete stops and destroys a VM of ours under the per-name lock, then
deletes its seed on the VM's node, or on every node when no VM of ours
was left. A hibernated VM of ours is Permanent, as in Create. The
Checker verifies each node concurrently (version, node status, ISO
storage, templates) and adds CertificateInvalid, CredentialsUnavailable,
StorageNotFound and TemplateNotFound to the shared reasons. The
ProviderHealth type comment gains proxmox.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

internal/provider/proxmox/proxmox_test.go

@@ -215,16 +215,6 @@ func TestWrapErr_carriesProviderNameOpAndID(t *testing.T) {
 	}
 }
 
-// TestStubs_answerTransient keeps a Proxy on this provider retrying, not
-// latched, until Delete is implemented in Phase 7.
-func TestStubs_answerTransient(t *testing.T) {
-	t.Parallel()
-	p := newProvider("proxmox-home", testConfig(), nil)
-	if err := p.Delete(context.Background(), "vms/150042/proxy-x"); !errors.Is(err, provider.ErrTransient) {
-		t.Errorf("delete error = %v, want ErrTransient", err)
-	}
-}
-
 func TestLockName_givesUpWithContextAsTransient(t *testing.T) {
 	t.Parallel()
 	p := newProvider("proxmox-home", testConfig(), nil)