feat(question_gen): register ActionRecognitionStrategy, replace temp VISUAL binding

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/unit/test_strategy.py

@@ -116,3 +116,27 @@ class TestSubPattern:
         )
         with pytest.raises(AttributeError):
             sp.name = "changed"
+
+
+class TestActionRecognitionRegistration:
+    """AR 策略注册后 get_strategy 返回特化实例。"""
+
+    def test_get_strategy_returns_ar_strategy(self):
+        """get_strategy('Action Recognition') 返回 ActionRecognitionStrategy。"""
+        from app.question_gen.strategy_action_recognition import ActionRecognitionStrategy
+
+        s = get_strategy("Action Recognition")
+        assert isinstance(s, ActionRecognitionStrategy)
+        assert s.task_type == "Action Recognition"
+        assert s.strategy_name == "ACTION_RECOGNITION"
+
+    def test_ar_not_base_strategy(self):
+        """get_strategy('Action Recognition') 不再返回 BaseTaskTypeStrategy。"""
+        s = get_strategy("Action Recognition")
+        assert not isinstance(s, BaseTaskTypeStrategy)
+
+    def test_other_types_still_base(self):
+        """其他题型仍返回 BaseTaskTypeStrategy。"""
+        for tt in ("Object Recognition", "Temporal Reasoning", "Spatial Reasoning"):
+            s = get_strategy(tt)
+            assert isinstance(s, BaseTaskTypeStrategy), f"{tt} 应该是 BaseTaskTypeStrategy"