xo-alloc2: + missing setup .*pp files

include/xo/alloc2/SetupAlloc2.hpp

@@ -0,0 +1,18 @@
+/** @file SetupAlloc2.hpp
+ *
+ *  @author Roland Conybeare, Feb 2026
+ **/
+
+#pragma once
+
+namespace xo {
+    namespace mm {
+        class SetupAlloc2 {
+        public:
+            /** Register alloc2 (facet,impl) combinations with Facet Registry **/
+            static bool register_facets();
+        };
+    }
+}
+
+/* end SetupAlloc2.hpp */