docs(html): 沉淀数据管理 iframe 预览布局契约

tests/test_html_page_service.py

@@ -61,6 +61,15 @@ class TestHtmlPageService(unittest.TestCase):
             with self.assertRaises(ValueError):
                 write_html_page("note.txt", "<html></html>")
 
+    def test_example_report_shell_embedded_preview_layout(self) -> None:
+        """守护 example-report.html：数据管理 iframe 预览布局基线不退化。"""
+        template = load_html_template("assets/html/example-report.html")
+        self.assertIn("overflow-x: hidden", template)
+        self.assertIn("min-width: 0", template)
+        self.assertIn("table-layout: fixed", template)
+        self.assertIn("overflow-wrap: anywhere", template)
+        self.assertNotIn("max-width:", template)
+
 
 if __name__ == "__main__":
     unittest.main()