xo-gc: + CollectorTypeRegistry for streamlined init

xo-expression2/include/xo/expression2/init_expression2.hpp

@@ -0,0 +1,21 @@
+/** @file init_expression2.hpp
+*
+ *  @author Roland Conybeare, Jan 2026
+ **/
+
+#pragma once
+
+#include <xo/subsys/Subsystem.hpp>
+
+namespace xo {
+    /* tag to represent the xo-expression2/ subsystem within ordered initialization */
+    enum S_expression2_tag {};
+
+    template <>
+    struct InitSubsys<S_expression2_tag> {
+        static void init();
+        static InitEvidence require();
+    };
+} /*namespace xo*/
+
+/* end init_expression2.hpp */