docs: precipitate Action/CRUD Lookup contract for skill authors

tests/test_docs_standards.py

@@ -341,6 +341,8 @@ class TestDocsStandards(unittest.TestCase):
             "表单与展示：稳定字段类型（宿主支持，须与 Action 对称）",
             "datetime_unix_seconds",
             "display_type: \"number\"",
+            "extra_column",
+            "{value} · {label}",
             "DEFAULT",
             "description",
             "文件 / 图片上传",
@@ -354,6 +356,9 @@ class TestDocsStandards(unittest.TestCase):
         for marker in (
             "inputSchema 与参数表单",
             "表单字段类型对照（须与 CRUD 对称）",
+            "跨表引用：Lookup",
+            "display_type: \"lookup\"",
+            "extra_column",
             "数据管理新增/编辑",
             "_jiangchang_columns.description",
             "datetime_unix_seconds",