fix(test): fix type-to-jump pagination compat and loading state race

- type-to-jump: use _setSectionTracks to inject test tracks instead of
  mutating the array returned by the paginated filteredTracks getter
  (unshift on a freshly built array was silently lost)
- error-states: combine set+read in single evaluate to prevent race
  with background library load() clearing the loading flag

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: pythoninthegrass

app/frontend/tests/error-states.spec.js

@@ -547,21 +547,19 @@ test.describe('Loading States', () => {
   });
 
   test('should track library loading state', async ({ page }) => {
-    // Set library to loading state
-    await page.evaluate(() => {
+    // Set and read in a single evaluate to avoid race with background load()
+    const loadingAfterSet = await page.evaluate(() => {
       window.Alpine.store('library').loading = true;
+      return window.Alpine.store('library').loading;
     });
+    expect(loadingAfterSet).toBe(true);
 
-    const libraryStore = await getAlpineStore(page, 'library');
-    expect(libraryStore.loading).toBe(true);
-
-    // Complete loading
-    await page.evaluate(() => {
+    // Complete loading and verify
+    const loadingAfterClear = await page.evaluate(() => {
       window.Alpine.store('library').loading = false;
+      return window.Alpine.store('library').loading;
     });
-
-    const updatedStore = await getAlpineStore(page, 'library');
-    expect(updatedStore.loading).toBe(false);
+    expect(loadingAfterClear).toBe(false);
   });
 });
 

app/frontend/tests/library-type-to-jump.spec.js

@@ -404,8 +404,9 @@ test.describe('Type-to-jump artist navigation (task-255)', () => {
     // because stripped "la's" starts with "la".
     await page.evaluate(() => {
       const library = window.Alpine.store('library');
-      // Insert in backend sort order: "La's" < "Lana Del Rey" alphabetically
-      library.tracks.unshift(
+      // Prepend test tracks via _setSectionTracks to bypass paginated getter
+      const existing = library.filteredTracks;
+      const testTracks = [
         {
           id: 9999,
           title: 'There She Goes',
@@ -422,8 +423,9 @@ test.describe('Type-to-jump artist navigation (task-255)', () => {
           duration: 180,
           filepath: '/music/test/decoy.mp3',
         },
-      );
-      library.applyFilters();
+      ];
+      library._setSectionTracks([...testTracks, ...existing]);
+      library.totalTracks = testTracks.length + existing.length;
       window.Alpine.store('ui').sortIgnoreWords = true;
       window.Alpine.store('ui').sortIgnoreWordsList = 'the, a, an, la, le, les, los, las, el';
     });