New DynamicViralPostingInvoker: takes runtime post-to target

include/spinscale/co/dynamicPostingInvoker.h

@@ -0,0 +1,36 @@
+#ifndef DYNAMIC_POSTING_INVOKER_H
+#define DYNAMIC_POSTING_INVOKER_H
+
+#include <stdexcept>
+
+#include <boost/asio/io_context.hpp>
+
+#include <spinscale/co/invokers.h>
+#include <spinscale/co/postingPromise.h>
+
+namespace sscl::co {
+
+/**	Fallback ThreadTag for DynamicViralPostingInvoker when ExplicitPostTarget is
+ *	omitted. Callers must always pass ExplicitPostTarget in production paths.
+ */
+struct DynamicPostTargetThreadTag
+{
+	static boost::asio::io_context &io_context()
+	{
+		throw std::runtime_error(
+			std::string(__func__)
+			+ ": ExplicitPostTarget required for DynamicViralPostingInvoker");
+	}
+};
+
+template<typename T>
+using DynamicPostingPromise =
+	TaggedPostingPromise<T, DynamicPostTargetThreadTag>;
+
+template<typename T>
+using DynamicViralPostingInvoker =
+	ViralPostingInvoker<DynamicPostingPromise, T>;
+
+} // namespace sscl::co
+
+#endif // DYNAMIC_POSTING_INVOKER_H

include/spinscale/co/postingPromise.h

@@ -223,8 +223,8 @@ struct PostingPromise
 		ExplicitPostTarget _calleePostTarget,
 		TailArgs &&...) noexcept
 	: returnValues(),
-	postBackStatus(*this),
-	calleePostTarget(std::move(_calleePostTarget))
+	calleePostTarget(std::move(_calleePostTarget)),
+	postBackStatus(*this)
 	{}
 
 	/**	Viral / free-function entry: post-TO uses ThreadTag default. */