window: preserve reading position across server reloads

After a server refresh the article list is rebuilt, which previously
always reloaded the WebView and reset the scroll position.

- Disable SingleSelection autoselect so store rebuilds don't trigger
  spurious selection changes.
- Skip the WebView reload in on_article_selected when the same article
  is re-selected, preserving the user's scroll position.
- When the previously-read article is no longer in the server response
  (read on another device), leave the sidebar unselected and keep the
  old article visible so the user can finish reading.
- Handle no-selection state in navigate_by() so j/k still work.
- Show a toast with the unread count after every successful fetch.

src/window.rs

@@ -206,6 +206,8 @@ pub mod imp {
         fn setup_list(&self) {
             let store = gio::ListStore::new::<ArticleObject>();
             let selection = gtk4::SingleSelection::new(Some(store.clone()));
+            selection.set_autoselect(false);
+            selection.set_can_unselect(true);
             *self.article_store.borrow_mut() = Some(store);
 
             let factory = gtk4::SignalListItemFactory::new();
@@ -255,12 +257,16 @@ pub mod imp {
             *self.mark_unread_guard.borrow_mut() = false;
 
             let article = obj.article().clone();
+            let same_article = self.current_article_id.borrow().as_deref() == Some(&*article.id);
             *self.current_article_id.borrow_mut() = Some(article.id.clone());
 
             self.article_menu_button.set_visible(true);
 
-            // Load in webview
+            // Skip WebView reload when re-selecting the same article (e.g. after
+            // a server refresh) so the user's scroll position is preserved.
+            if !same_article {
                 self.load_article_in_webview(&article);
+            }
             obj.set_unread(false);
         }
 
@@ -715,39 +721,64 @@ pub mod imp {
                                 store.append(&ArticleObject::new(a.clone()));
                             }
 
-                            // Save cache and clean up unreferenced images.
-                            let sel_id = saved_id.as_deref().unwrap_or("");
-                            crate::cache::save(&articles, sel_id);
                             crate::image_cache::cleanup(&articles);
 
-                            if store.n_items() == 0 {
+                            let n = store.n_items();
+                            if n == 0 {
                                 imp.sidebar_content.set_visible_child_name("empty");
                                 *imp.current_article_id.borrow_mut() = None;
                                 imp.article_menu_button.set_visible(false);
                                 imp.content_stack.set_visible_child_name("empty");
+                                crate::cache::save(&articles, "");
                             } else {
-                                // Try to re-select the same article; fall back to first.
+                                // Try to re-select the same article the user was reading.
-                                let mut select_idx = 0u32;
+                                let found_idx = saved_id.as_ref().and_then(|id| {
-                                if let Some(ref id) = saved_id {
+                                    (0..n).find(|&i| {
-                                    for i in 0..store.n_items() {
+                                        store.item(i).and_downcast::<ArticleObject>()
-                                        if store.item(i).and_downcast::<ArticleObject>()
                                             .map(|o| o.article().id == *id)
                                             .unwrap_or(false)
-                                        {
+                                    })
-                                            select_idx = i;
+                                });
-                                            break;
+
-                                        }
+                                if let Some(idx) = found_idx {
-                                    }
+                                    // Article still unread — re-select it without
-                                }
+                                    // reloading the WebView (preserves scroll position).
                                     *imp.mark_unread_guard.borrow_mut() = true;
-                                sel.set_selected(select_idx);
+                                    sel.set_selected(idx);
                                     imp.article_list_view.scroll_to(
-                                    select_idx,
+                                        idx,
                                         gtk4::ListScrollFlags::SELECT,
                                         None,
                                     );
+                                    crate::cache::save(&articles,
+                                        saved_id.as_deref().unwrap_or(""));
+                                } else if saved_id.is_some() {
+                                    // Article was read elsewhere — keep it in the
+                                    // WebView so the user can finish reading but
+                                    // leave the sidebar list unselected.
+                                    crate::cache::save(&articles, "");
+                                } else {
+                                    // No previous article (first load) — select the
+                                    // first article.
+                                    sel.set_selected(0);
+                                    imp.article_list_view.scroll_to(
+                                        0,
+                                        gtk4::ListScrollFlags::SELECT,
+                                        None,
+                                    );
+                                    crate::cache::save(&articles, "");
+                                }
                                 imp.sidebar_content.set_visible_child_name("list");
                             }
+
+                            // Always notify the user that the fetch finished.
+                            let msg = if n == 1 {
+                                String::from("1 unread article")
+                            } else {
+                                format!("{n} unread articles")
+                            };
+                            let toast = libadwaita::Toast::new(&msg);
+                            imp.toast_overlay.add_toast(toast);
                         }
                         Err(e) => {
                             // If we already have cached articles, just show a toast.
@@ -846,7 +877,10 @@ pub mod imp {
             let n = sel.n_items();
             if n == 0 { return }
             let current = sel.selected();
-            let next = if delta > 0 {
+            let next = if current == gtk4::INVALID_LIST_POSITION {
+                // Nothing selected — pick the first or last article.
+                if delta > 0 { 0 } else { n - 1 }
+            } else if delta > 0 {
                 (current + 1).min(n - 1)
             } else {
                 current.saturating_sub(1)