fix(iced): add viewer keyboard navigation and wire lazy loading

hcie-iced-app/crates/hcie-iced-gui/src/app.rs

@@ -519,6 +519,9 @@ pub enum Message {
     ViewerOpenFile(std::path::PathBuf),
     ViewerRefresh,
     ViewerFullscreen(bool),
+    ViewerPrev,
+    ViewerNext,
+    ViewerEnter,
 }
 
 /// Convert a FilterType enum to the engine's string filter ID.
@@ -3350,10 +3353,36 @@ impl HcieIcedApp {
                     }
                 }
             }
+            Message::ViewerPrev => {
+                if self.viewer_active {
+                    self.viewer_state.prev_image();
+                    self.viewer_state.load_preview();
+                }
+            }
+            Message::ViewerNext => {
+                if self.viewer_active {
+                    self.viewer_state.next_image();
+                    self.viewer_state.load_preview();
+                }
+            }
+            Message::ViewerEnter => {
+                if self.viewer_active && !self.viewer_state.images.is_empty() {
+                    let path = self.viewer_state.images[self.viewer_state.active_image_idx].clone();
+                    return Task::perform(async move {}, move |_| Message::ViewerOpenFile(path.clone()));
+                }
+            }
 
             Message::NoOp => {}
         }
 
+        // Lazy-load thumbnails when viewer is active (max LAZY_LOAD_BUDGET per frame)
+        if self.viewer_active {
+            let batch = crate::viewer::thumbnail_grid::next_load_batch(&self.viewer_state);
+            for path in batch {
+                self.viewer_state.load_thumbnail(&path);
+            }
+        }
+
         Task::none()
     }
 
@@ -3584,13 +3613,20 @@ impl HcieIcedApp {
                 iced::keyboard::Key::Character(ref c) if c.as_str() == "i" && ctrl && shift => {
                     Some(Message::SelectInverse)
                 }
-                // Escape = close menu, cancel dialog, deselect, or cancel crop
+                // Arrow keys — viewer navigation or no-op
-                iced::keyboard::Key::Named(iced::keyboard::key::Named::Escape) => {
+                iced::keyboard::Key::Named(iced::keyboard::key::Named::ArrowLeft) => {
-                    Some(Message::MenuClose) // Crop cancel handled in update()
+                    Some(Message::ViewerPrev)
                 }
-                // Enter = confirm crop
+                iced::keyboard::Key::Named(iced::keyboard::key::Named::ArrowRight) => {
+                    Some(Message::ViewerNext)
+                }
+                // Escape = exit viewer, close menu, cancel dialog, deselect, or cancel crop
+                iced::keyboard::Key::Named(iced::keyboard::key::Named::Escape) => {
+                    Some(Message::ViewerToggle)
+                }
+                // Enter = open file in viewer, or confirm crop
                 iced::keyboard::Key::Named(iced::keyboard::key::Named::Enter) => {
-                    Some(Message::CropConfirm) // Crop confirm handled in update()
+                    Some(Message::ViewerEnter)
                 }
                 _ => None,
             }