refactor(core): delegate GetByLevel to QueryOperationService

ContentService.GetByLevel now delegates to QueryOperationService,
continuing Phase 2 query operation extraction.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/Umbraco.Core/Services/ContentService.cs

@@ -614,14 +614,7 @@ public class ContentService : RepositoryService, IContentService
     /// <returns>An Enumerable list of <see cref="IContent" /> objects</returns>
     /// <remarks>Contrary to most methods, this method filters out trashed content items.</remarks>
     public IEnumerable<IContent> GetByLevel(int level)
-    {
-        using (ICoreScope scope = ScopeProvider.CreateCoreScope(autoComplete: true))
-        {
-            scope.ReadLock(Constants.Locks.ContentTree);
-            IQuery<IContent>? query = Query<IContent>().Where(x => x.Level == level && x.Trashed == false);
-            return _documentRepository.Get(query);
-        }
-    }
+        => QueryOperationService.GetByLevel(level);
 
     /// <summary>
     ///     Gets a specific version of an <see cref="IContent" /> item.

tests/Umbraco.Tests.Integration/Umbraco.Infrastructure/Services/ContentServiceRefactoringTests.cs

@@ -746,6 +746,24 @@ internal sealed class ContentServiceRefactoringTests : UmbracoIntegrationTestWit
         Assert.That(facadeCount, Is.EqualTo(directCount));
     }
 
+    /// <summary>
+    /// Phase 2 Test: Verifies GetByLevel() via facade returns same result as direct service call.
+    /// </summary>
+    [Test]
+    public void GetByLevel_ViaFacade_ReturnsEquivalentResultToDirectService()
+    {
+        // Arrange
+        var queryService = GetRequiredService<IContentQueryOperationService>();
+
+        // Act
+        var facadeItems = ContentService.GetByLevel(1).ToList();
+        var directItems = queryService.GetByLevel(1).ToList();
+
+        // Assert
+        Assert.That(facadeItems.Count, Is.EqualTo(directItems.Count));
+        Assert.That(facadeItems.Select(x => x.Id), Is.EquivalentTo(directItems.Select(x => x.Id)));
+    }
+
     #endregion
 
     /// <summary>