perf: reduce queue and extension runtime overhead

test/models_and_utils_test.dart

@@ -755,6 +755,7 @@ void main() {
       expect(lookup.queuedCount, 3);
       expect(lookup.activeDownloadsCount, 1);
       expect(lookup.finalizingCount, 1);
+      expect(lookup.notCompletedItemIds, ['queued', 'active', 'finalizing']);
 
       final next = List<DownloadItem>.from(previous);
       next[2] = previous[2].copyWith(status: DownloadStatus.completed);
@@ -769,6 +770,22 @@ void main() {
       expect(updated.finalizingCount, 0);
       expect(identical(updated.indexByItemId, lookup.indexByItemId), isTrue);
       expect(identical(updated.itemIds, lookup.itemIds), isTrue);
+      expect(updated.notCompletedItemIds, ['queued', 'active']);
+
+      final progressOnly = List<DownloadItem>.from(next);
+      progressOnly[1] = next[1].copyWith(progress: 0.5);
+      final progressUpdated = updated.updatedForIndices(
+        previousItems: next,
+        nextItems: progressOnly,
+        changedIndices: const [1],
+      );
+      expect(
+        identical(
+          progressUpdated.notCompletedItemIds,
+          updated.notCompletedItemIds,
+        ),
+        isTrue,
+      );
     });
   });
 

test/music_player_media_metadata_test.dart

@@ -104,4 +104,26 @@ void main() {
     expect(calls, 1);
     expect(metadata['title'], 'Instrumental');
   });
+
+  test('shuffle candidate selection excludes recent tracks', () {
+    expect(
+      buildShuffleCandidatePool(
+        mediaCount: 6,
+        currentIndex: 2,
+        recentIndices: const [0, 1, 3],
+      ),
+      [4, 5],
+    );
+  });
+
+  test('shuffle candidate selection resets after exhausting the pool', () {
+    expect(
+      buildShuffleCandidatePool(
+        mediaCount: 4,
+        currentIndex: 2,
+        recentIndices: const [0, 1, 3],
+      ),
+      [0, 1, 3],
+    );
+  });
 }