Wire up step buttons: Browse, preset cards, output directory picker

- Browse Files button triggers win.add-files action
- Add More button in loaded state triggers win.add-files action
- Preset card activation (click) advances to next wizard step
- Custom workflow card activation advances to next step
- Choose output folder button opens folder dialog
- Output step shows current image count when navigated to
- Clean up dead code in update_count_in_box

pixstrip-gtk/src/steps/step_images.rs

@@ -72,6 +72,7 @@ fn build_empty_state() -> gtk::Box {
         .label("Browse Files")
         .tooltip_text("Add image files (Ctrl+O)")
         .halign(gtk::Align::Center)
+        .action_name("win.add-files")
         .build();
     browse_button.add_css_class("suggested-action");
     browse_button.add_css_class("pill");
@@ -112,6 +113,7 @@ fn build_loaded_state() -> gtk::Box {
     let add_button = gtk::Button::builder()
         .icon_name("list-add-symbolic")
         .tooltip_text("Add more images")
+        .action_name("win.add-files")
         .build();
     add_button.add_css_class("flat");
 

pixstrip-gtk/src/steps/step_output.rs

@@ -46,6 +46,7 @@ pub fn build_output_page() -> adw::NavigationPage {
         .icon_name("folder-open-symbolic")
         .tooltip_text("Choose output folder")
         .valign(gtk::Align::Center)
+        .action_name("win.choose-output")
         .build();
     choose_button.add_css_class("flat");
     output_row.add_suffix(&choose_button);

pixstrip-gtk/src/steps/step_workflow.rs

@@ -36,6 +36,11 @@ pub fn build_workflow_page() -> adw::NavigationPage {
         builtin_flow.append(&card);
     }
 
+    // When a preset card is activated, advance to the next step
+    builtin_flow.connect_child_activated(|flow, _child| {
+        flow.activate_action("win.next-step", None).ok();
+    });
+
     builtin_group.add(&builtin_flow);
     content.append(&builtin_group);
 
@@ -52,6 +57,9 @@ pub fn build_workflow_page() -> adw::NavigationPage {
         .min_children_per_line(2)
         .build();
     custom_flow.append(&custom_card);
+    custom_flow.connect_child_activated(|flow, _child| {
+        flow.activate_action("win.next-step", None).ok();
+    });
     custom_group.add(&custom_flow);
     content.append(&custom_group);