add unit test coverage for UndoRedoService, WorkflowConsoleService, and NotificationService

[mengw15]

Task Summary

Three workspace services whose specs are near-empty (each asserts little beyond creation) while codecov sits well below their real surface. Extend each spec. Vitest; see frontend/TESTING.md (reuse Stub…Service doubles / useValue + vi.fn()).

Behavior to add

UndoRedoService (frontend/src/app/workspace/service/undo-redo/undo-redo.service.ts, codecov ~67%)

• Drive via setUndoManager(...) with a Y.UndoManager double (or a real one over a Y.Doc): undoAction / redoAction call undo / redo only when canUndo / canRedo; canUndo / canRedo / getUndoLength / getRedoLength reflect the manager; clearUndoStack / clearRedoStack clear it; enableWorkFlowModification / disableWorkFlowModification toggle the guard so actions become no-ops when disabled.

WorkflowConsoleService (frontend/src/app/workspace/service/workflow-console/workflow-console.service.ts, codecov ~68%)

• getConsoleMessages / hasConsoleMessages after messages arrive; clearConsoleMessages empties the store and pushes an update on getConsoleMessageUpdateStream; registerAutoClearConsoleMessages clears on the configured trigger.

NotificationService (frontend/src/app/common/service/notification/notification.service.ts, codecov ~47%)

• Inject NzMessageService + NzNotificationService doubles (vi.fn()). Assert success / error / info / warning / blank delegate to the right notification type with the given title/content/options, and loading / remove delegate to the message service.

Task Type

• Refactor / Cleanup
• DevOps / Deployment / CI
• Testing / QA
• Documentation
• Performance
• Other