fix: run_gates must use current_tree after video resample

tests/unit/test_pipeline_v2_tree_fix.py

@@ -0,0 +1,25 @@
+"""守卫 gate tree 错配 bug：run_gates 必须用 current_tree（换视频后的当前树）。"""
+
+import ast
+from pathlib import Path
+
+_PIPELINE = Path(__file__).resolve().parents[2] / "app" / "question_gen" / "pipeline_v2.py"
+
+
+def _find_run_gates_tree_arg() -> str:
+    """解析 pipeline_v2.py，返回 run_gates 调用中 tree= 关键字实参的变量名。"""
+    tree_src = ast.parse(_PIPELINE.read_text(encoding="utf-8"))
+    for node in ast.walk(tree_src):
+        if isinstance(node, ast.Call):
+            func = node.func
+            name = getattr(func, "id", None) or getattr(func, "attr", None)
+            if name == "run_gates":
+                for kw in node.keywords:
+                    if kw.arg == "tree":
+                        assert isinstance(kw.value, ast.Name)
+                        return kw.value.id
+    raise AssertionError("未找到 run_gates 的 tree= 关键字实参")
+
+
+def test_run_gates_uses_current_tree():
+    assert _find_run_gates_tree_arg() == "current_tree"