acquisition: drive a DataSource from the registry; --source and --source-opt

src/ui_probe.cpp

@@ -5411,7 +5411,7 @@ gboolean help_probe(gpointer user) {
   App* a = static_cast<App*>(user);
   const HelpReport report = help_self_check();
   const std::string session =
-      layout_path(a->model->config().server, a->model->config().port);
+      layout_path(a->model->config().session_host(), a->model->config().session_port());
 
   // The manual is *launched* here and read no further: it opens in another process (Yelp, through
   // the `help:` URI) and neither it nor this box can draw a window for it, so there is nothing to