xo-alloc2: refactor - explicit AllocHeader class

xo-alloc2/include/xo/alloc2/gc/object_age.hpp

@@ -0,0 +1,32 @@
+/** @file object_age.hpp
+ *
+ *  @author Roland Conybeare, Dec 2025
+ **/
+
+#pragma once
+
+#include <cstdint>
+
+namespace xo {
+    namespace mm {
+        /** hard maximum remembered object age **/
+        static constexpr uint32_t c_max_object_age = 127;
+
+        /** @class object_age
+         *  @brief type-safe object age
+         *
+         *  Object age measured in number of garbage collections survived.
+         **/
+        struct object_age {
+            using value_type = std::uint32_t;
+
+            explicit object_age(value_type x) : value_{x} {}
+
+            operator value_type() const { return value_; }
+
+            std::uint32_t value_;
+        };
+    }
+}
+
+/* end object_age.hpp */