fix: require usable recipe task results

tests/test_background_tasks.py

@@ -65,6 +65,14 @@ def test_deferred_task_answers_are_rejected():
         "Nepal began flood recovery, Venezuela signed an oil agreement, and Iran resumed talks."
     )
 
+    recipe_worker = TaskWorker("test", "Give me a buttercream recipe")
+    assert recipe_worker._is_underfilled_recipe_answer(
+        "Use butter, powdered sugar, vanilla, and milk, then mix until smooth."
+    )
+    assert not recipe_worker._is_underfilled_recipe_answer(
+        "Beat one cup butter with three cups powdered sugar and two tablespoons milk until smooth."
+    )
+
 
 def test_task_event_directories_are_isolated(tmp_path):
     first = TaskRegistry(tmp_path / "room-one")