ui: the sidebar's tabs become one dock; Measure and Signals by keyboard section; session keeps the dock's state

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

src/ui_tour.cpp

@@ -422,11 +422,9 @@ void start_tour(App& app) {
     app.settings.tour_seen = true;
     (void)save_settings(app.settings);
   }
-  // The sidebar's own stack, so a stop can name the page it stands on. Set here and not in
-  // `build_tour()`: the overlay is inserted above the window's content *before* `App::side_stack` is
-  // assigned, so the member does not exist yet at build time -- and the walk cannot start before the
-  // window is up anyway.
-  app.tour.page_stack = app.side_stack;
+  // The main window has no page stack any more (the dock is one scroller): `page_stack` stays null, so
+  // a stop's `page` selects nothing and a stop whose target is unmapped is dropped. The slide-over hook
+  // that lets a stop open the trigger page is the next step's.
   // The whole table, in walk order: `tour_begin()` drops the stops whose surface is not on screen.
   std::vector<TourStop> stops;
   stops.reserve(kTourStepCount);
@@ -486,8 +484,7 @@ constexpr FigureSurface kFigureSurfaces[] = {
     {"trigger_summary", &App::trigger_summary},
     {"trigger_panel", &App::trigger_panel},
     {"signal_list", &App::signal_list},
-    {"side_switcher", &App::side_switcher},
-    {"side_stack", &App::side_stack},
+    {"side_stack", &App::side_box},
     {"window_button", &App::window_button},
     {"status_label", &App::status_label},
     {"header_bar", &App::toolbar},