source: a synthetic probe kind, and sessions that remember their source kind

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/ui_app.hpp

@@ -29,6 +29,7 @@
 #include "plot_host.hpp"
 #include "search.hpp"
 #include "settings.hpp"
+#include "source/source_config.hpp"
 #include "ui_prefs.hpp"
 #include "shortcuts.hpp"
 #include "status_text.hpp"
@@ -837,6 +838,11 @@ struct App {
   /// chooser needs both to reconnect to a multicast source from a stored row.
   std::string source_multicast;
   std::string source_interface;
+  /// The source kind and its settings, so the session can say which kind it belongs to, and the
+  /// words that name the source in dialogs (`host:port` for UDPS, `<kind> <identity>` otherwise).
+  std::string source_kind = "udps";
+  SourceConfig source_opts;
+  std::string source_title;
   guint layout_save_source = 0;
   bool layout_loaded = false;
   unsigned signal_generation = ~0u;