refactor(controller): extract shared mirror-deletion and naming helpers

Replace the triplicated ownership-verified delete guard with deleteOwnedMirror, and hand-built controller-name strings with gvkControllerName. Use constants.Domain/ControllerName over magic strings and maps.Copy/Clone for plain copy loops. Behaviour-preserving; tests green.

pkg/controller/naming.go

@@ -0,0 +1,18 @@
+// Package controller implements the kubemirror reconciliation logic.
+package controller
+
+import "k8s.io/apimachinery/pkg/runtime/schema"
+
+// gvkControllerName builds the unique controller-runtime controller name for a
+// GVK. Including version and group avoids collisions across API versions, e.g.
+// "HorizontalPodAutoscaler.v1.autoscaling" or "Secret.v1." (empty group for
+// core resources). Source and mirror reconcilers for the same GVK must differ,
+// so mirror controllers get a "-mirror" suffix. This is the single source of
+// truth for the convention shared by both reconcilers.
+func gvkControllerName(gvk schema.GroupVersionKind, mirror bool) string {
+	name := gvk.Kind + "." + gvk.Version + "." + gvk.Group
+	if mirror {
+		name += "-mirror"
+	}
+	return name
+}