migrate from std::filesystem::path to io::path (WIP)

src/io/path.cpp

@@ -0,0 +1,11 @@
+#include "path.hpp"
+
+#include <stdexcept>
+
+using namespace io;
+
+void path::checkValid() const {
+    if (colonPos == std::string::npos) {
+        throw std::runtime_error("path entry point is not specified: " + str);
+    }
+}