fix sort resetting to default when toggling series collapse (#3031)

Author: acx10

booklore-ui/src/app/features/book/components/book-browser/book-browser-query-params.service.ts

@@ -287,7 +287,7 @@ export class BookBrowserQueryParamsService {
     }
 
     const currentParams = this.activatedRoute.snapshot.queryParams;
-    const changed = Object.keys(queryParams).some(k => currentParams[k] !== queryParams[k]);
+    const changed = Object.keys(queryParams).some(k => (queryParams[k] ?? undefined) !== (currentParams[k] ?? undefined));
 
     if (changed) {
       const mergedParams = {...currentParams, ...queryParams};

booklore-ui/src/app/features/book/components/book-browser/book-browser.component.ts

@@ -470,8 +470,13 @@ export class BookBrowserComponent implements OnInit, AfterViewInit, OnDestroy {
       this.visibleSortOptions = visibleFields.map(f => sortOptionsByField.get(f)).filter((o): o is SortOption => !!o);
 
 
-      // Only update sort criteria if they actually changed to avoid resetting popover/CDK state
-      if (!this.areSortCriteriaEqual(this.bookSorter.selectedSortCriteria, parseResult.sortCriteria)) {
+      // Only update sort criteria if they actually changed to avoid resetting popover/CDK state.
+      // Skip preference-based sort re-derivation when sort is already established (prevents
+      // userState$ emissions from non-sort preference changes like seriesCollapsed from
+      // resetting the sort during the race window before syncQueryParams writes to URL).
+      const sortFromUrl = !!queryParamMap.get('sort');
+      const sortNotYetEstablished = this.bookSorter.selectedSortCriteria.length === 0;
+      if ((sortFromUrl || sortNotYetEstablished) && !this.areSortCriteriaEqual(this.bookSorter.selectedSortCriteria, parseResult.sortCriteria)) {
         this.bookSorter.setSortCriteria(parseResult.sortCriteria);
       }
       this.currentViewMode = parseResult.viewMode;