fix: keep cross_segment rule single-dimension, guard no-absent-events

tests/unit/test_ar_sub_pattern_counterfactual.py

@@ -2,14 +2,13 @@
 
 from app.question_gen.strategy_action_recognition import AR_SUB_PATTERNS
 
-_REQUIRED = ["真实", "单一维度"]  # 每个 distractor_rules 都需强调 grounded + 单维
-
 
 def test_all_sub_patterns_enforce_single_dimension_counterfactual():
     for sp in AR_SUB_PATTERNS:
         rules = sp.distractor_rules
         assert "真实" in rules, sp.name  # 干扰项须真实发生
         assert ("单一维度" in rules or "只在" in rules or "仅在" in rules), sp.name
+        assert ("缺席" in rules or "未出现" in rules or "凭空" in rules), sp.name
 
 
 def test_sub_pattern_count_unchanged():