proxmox: review fixes, real-host validation record, changelog

Phase 10. Two review passes (go-operator-reviewer, /code-review high)
over the branch, recorded in docs/reviews/2026-09-23-proxmox-provider-review/:
9 findings fixed, 3 accepted as documented limits, 7 rejected with a
reason.

- Delete removes the seed between the stop and the destroy, so a failed
  seed delete leaves the VM for the next Delete instead of leaking the
  ISO; a Permanent refusal on the every-node path fails the call.
- Create skips a probe VMID whose listed name is someone else's without
  waiting on its lock.
- The three answers Phase 0 never captured are fixtures now: a missing
  storage is a 400 (the Checker reports StorageNotFound), a hibernated
  VM is destroyable (Delete destroys ours), a paused VM stops.
- TestProxmox_lifecycle and TestProxmoxCheck_realHost passed on pv1-1
  (PVE 9.2.20); the docs record the run and drop "not yet run".

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

internal/provider/proxmox/errors_test.go

@@ -93,6 +93,7 @@ func TestAPIError_matchers(t *testing.T) {
 		"isAlreadyExists":      isAlreadyExists,
 		"isAgentNotRunning":    isAgentNotRunning,
 		"isAgentNotConfigured": isAgentNotConfigured,
+		"isNoSuchStorage":      isNoSuchStorage,
 		"isVMNotRunning":       isVMNotRunning,
 	}
 	tests := []struct {
@@ -104,6 +105,7 @@ func TestAPIError_matchers(t *testing.T) {
 		{"err_destroy_missing", "isNotExist"},
 		{"err_config_while_clone_locked", "isLocked"},
 		{"err_newid_in_use", "isAlreadyExists"},
+		{"storage_status_missing", "isNoSuchStorage"},
 		{"err_agent_not_running", "isAgentNotRunning"},
 		{"err_agent_vm_stopped", "isAgentNotConfigured"},
 		{"err_agent_vm_stopped_agent_enabled", "isVMNotRunning"},
@@ -184,12 +186,16 @@ func TestAPIError_errorString(t *testing.T) {
 	}
 }
 
-func TestPermanentfAndTransientf(t *testing.T) {
+func TestPermanentf_wrapsClassWithMessage(t *testing.T) {
 	t.Parallel()
 	perm := permanentf("node %q missing", "x")
 	if !errors.Is(perm, provider.ErrPermanent) || perm.Error() != `provider: permanent error: node "x" missing` {
 		t.Errorf("permanentf() = %q, want ErrPermanent with the message", perm)
 	}
+}
+
+func TestTransientf_wrapsClassWithMessage(t *testing.T) {
+	t.Parallel()
 	trans := transientf("retry %d", 3)
 	if !errors.Is(trans, provider.ErrTransient) || trans.Error() != "provider: transient error: retry 3" {
 		t.Errorf("transientf() = %q, want ErrTransient with the message", trans)