feat: add supports_flip/flip_axis to SubPattern for Phase B flip gate

app/question_gen/strategy.py

@@ -49,6 +49,8 @@ class SubPattern:
         positive_examples: VME 原题 few-shot 示范。
         negative_examples: 反面示例。
         distractor_rules: 干扰项构造规则。
+        supports_flip: 是否支持配对翻转门（Phase B 用，默认 False）。
+        flip_axis: 翻转轴（"before/after" | "first/last"），None 表示不翻转。
     """
 
     name: str
@@ -59,6 +61,8 @@ class SubPattern:
     positive_examples: list[dict] = field(default_factory=list)
     negative_examples: list[dict] = field(default_factory=list)
     distractor_rules: str = ""
+    supports_flip: bool = False
+    flip_axis: str | None = None
 
 
 # ---------------------------------------------------------------------------

app/question_gen/strategy_action_recognition.py

@@ -85,6 +85,8 @@ _TEMPORAL_REASONING_FAILURE = SubPattern(
         "即同一组真实事件的错误排列或错误的第 N 次定位。"
         "严禁使用视频中未出现的缺席事件作为干扰项。"
     ),
+    supports_flip=True,
+    flip_axis="before/after",
 )
 
 _SEMANTIC_RIGIDITY = SubPattern(
@@ -183,6 +185,8 @@ _CROSS_SEGMENT_ENTITY_TRACKING = SubPattern(
         "仅在【动作主体】这一单一维度上与正解不同。"
         "严禁编造任何实体未做过的缺席动作。"
     ),
+    supports_flip=True,
+    flip_axis="first/last",
 )
 
 _EVIDENCE_GAP_CONFABULATION = SubPattern(

tests/unit/test_sub_pattern_flip.py

@@ -0,0 +1,33 @@
+"""SubPattern.supports_flip/flip_axis 默认值 + AR 两个子模式的翻转声明。"""
+
+from app.question_gen.strategy import SubPattern
+from app.question_gen.strategy_action_recognition import AR_SUB_PATTERNS
+
+_FLIP_EXPECTED = {
+    "temporal_reasoning_failure": "before/after",
+    "cross_segment_entity_tracking": "first/last",
+}
+
+
+def test_sub_pattern_defaults_no_flip():
+    sp = SubPattern(
+        name="x", weight=1.0, sampling_level_override=None,
+        constraint_override=None, instruction="i",
+    )
+    assert sp.supports_flip is False
+    assert sp.flip_axis is None
+
+
+def test_ar_flip_declarations():
+    by_name = {sp.name: sp for sp in AR_SUB_PATTERNS}
+    for name, axis in _FLIP_EXPECTED.items():
+        assert by_name[name].supports_flip is True, name
+        assert by_name[name].flip_axis == axis, name
+
+
+def test_other_ar_sub_patterns_keep_defaults():
+    for sp in AR_SUB_PATTERNS:
+        if sp.name in _FLIP_EXPECTED:
+            continue
+        assert sp.supports_flip is False, sp.name
+        assert sp.flip_axis is None, sp.name