Refactor workbench into task-based UI shell

backend/tests/test_sprint39_frontend_orchestration_hooks.py

@@ -35,10 +35,10 @@ def test_app_entrypoint_has_clean_encoding_and_react_imports() -> None:
     app = app_path.read_text(encoding="utf-8")
 
     assert not app_bytes.startswith(b"\xef\xbb\xbf")
-    assert "import { useMemo } from 'react'" in app
+    assert "import { useMemo, useState } from 'react'" in app
     assert "FormEvent" not in app
     assert "useEffect" not in app
-    assert "useState" not in app
+    assert "const [activeWorkspace, setActiveWorkspace] = useState<WorkspaceKey>('overview')" in app
 
 
 def test_demo_workflow_hook_owns_demo_api_and_cross_module_selection() -> None: