Add accessible labels to thumbnail grid and toolbar

pixstrip-gtk/src/steps/step_images.rs

@@ -685,6 +685,9 @@ fn build_loaded_state(state: &AppState) -> gtk::Box {
         .max_columns(10)
         .build();
     grid_view.add_css_class("thumbnail-grid");
+    grid_view.update_property(&[
+        gtk::accessible::Property::Label("Image thumbnail grid. Use arrow keys to navigate."),
+    ]);
 
     let scrolled = gtk::ScrolledWindow::builder()
         .hscrollbar_policy(gtk::PolicyType::Never)
@@ -755,6 +758,10 @@ fn build_loaded_state(state: &AppState) -> gtk::Box {
     toolbar.append(&add_button);
     toolbar.append(&clear_button);
 
+    toolbar.update_property(&[
+        gtk::accessible::Property::Label("Image toolbar with count, selection, and add controls"),
+    ]);
+
     let separator = gtk::Separator::new(gtk::Orientation::Horizontal);
 
     container.append(&toolbar);