ui: the Source badge, and the source panels as slide-over pages

src/ui.cpp

@@ -5072,8 +5072,6 @@ void on_activate(GtkApplication* application, gpointer user) {
   }
   // The slide-over panel: an overlay child of the plot, above the GL area.
   build_slideover(*app);
-  // The badge bar reads `trigger_toggle`, which `build_toolbar()` made above.
-  build_badge_bar(*app);
 
   // The size the window opens at, stated in code as well as in the `.ui`: `default-width` there is the
   // size it *asks* for, and a window whose content has a larger minimum opens at that minimum instead --
@@ -5222,6 +5220,9 @@ void on_activate(GtkApplication* application, gpointer user) {
   // are hidden first and kept hidden for the pages this call adds.
   keep_tabs_icon_free(*app);
   build_source_panels(*app);
+  // The badge bar reads `trigger_toggle` (made by `build_toolbar()` above) and the source's pages, which
+  // `build_source_panels()` has just registered: the Source badge opens the first of them.
+  build_badge_bar(*app);
 
   // The left side is the events pane *and* the plot, in one row: the pane is a column of its own
   // (the item's "collapsable pane on the left"), revealed by trigger mode.