fix(chv): _load_playwright 须返回 sync_playwright() 实例

返回函数本身则无 __enter__，真实启动路径从未跑通过（P2 假实现
掩盖；2026-11-08 构建 #8 驱动 live 抓到）。回归测试钉死该契约。

cloud/tests/test_chv_opt_stage3.py

@@ -234,6 +234,28 @@ class ScreenshotTest(unittest.TestCase):
 
 
 class CdpAndStatusTest(unittest.TestCase):
+    def test_load_playwright_returns_context_manager(self):
+        # 2026-11-08 live 根因：_load_playwright 返回 sync_playwright
+        # 函数本身（无 __enter__），真实启动路径从未跑通过。
+        import sys
+        import types
+
+        class FakeCM:
+            def __enter__(self):
+                return self
+
+            def __exit__(self, *exc):
+                return False
+
+        fake_mod = types.ModuleType("playwright.sync_api")
+        fake_mod.sync_playwright = lambda: FakeCM()
+        with mock.patch.dict(sys.modules,
+                             {"playwright.sync_api": fake_mod}):
+            cm = BROWSER._load_playwright()
+        self.assertTrue(hasattr(cm, "__enter__"))
+        self.assertTrue(hasattr(cm, "__exit__"))
+        self.assertIsInstance(cm, FakeCM)
+
     def test_cdp_returns_websocket_url(self):
         with tempfile.TemporaryDirectory() as tmp:
             agent, _c, _h = _agent([FakePage()], tmp)