fix: auth 测试改用 monkeypatch.setattr，MarkdownSplitter 跳过代码块内标题识别

tests/test_auth.py

@@ -15,35 +15,32 @@ class TestVerifyApiKey:
         """未设置环境变量时跳过认证."""
         monkeypatch.setenv("MD_VECTOR_API_KEY", "")
         import src.server.auth as auth
-        auth._get_expected_api_key = lambda: ""
+        monkeypatch.setattr(auth, "_get_expected_api_key", lambda: "")
         result = verify_api_key(x_api_key=None)
         assert result is True
 
     def test_rejects_when_key_required_but_not_provided(self, monkeypatch):
         """已设置密钥但请求未提供."""
         import src.server.auth as auth
-        auth._get_expected_api_key = lambda: "secret123"
+        monkeypatch.setattr(auth, "_get_expected_api_key", lambda: "secret123")
         with pytest.raises(HTTPException) as exc:
             verify_api_key(x_api_key=None)
         assert exc.value.status_code == 401
-        auth._get_expected_api_key = auth._make_get_api_key()
 
     def test_rejects_wrong_key(self, monkeypatch):
         """错误的密钥被拒绝."""
         import src.server.auth as auth
-        auth._get_expected_api_key = lambda: "secret123"
+        monkeypatch.setattr(auth, "_get_expected_api_key", lambda: "secret123")
         with pytest.raises(HTTPException) as exc:
             verify_api_key(x_api_key="wrong-key")
         assert exc.value.status_code == 401
-        auth._get_expected_api_key = auth._make_get_api_key()
 
     def test_accepts_correct_key(self, monkeypatch):
         """正确的密钥通过认证."""
         import src.server.auth as auth
-        auth._get_expected_api_key = lambda: "secret123"
+        monkeypatch.setattr(auth, "_get_expected_api_key", lambda: "secret123")
         result = verify_api_key(x_api_key="secret123")
         assert result is True
-        auth._get_expected_api_key = auth._make_get_api_key()
 
 
 class TestRateLimiter: