Fix remaining pre-commit issues and add missing branch coverage

- Remove unused Union import in win32/utilities.py, use | syntax
- Add test for get_ipython() returning None (covers 43->52 branch)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: BabyChrist666

src/mcp/os/win32/utilities.py

@@ -5,7 +5,7 @@
 import subprocess
 import sys
 from pathlib import Path
-from typing import BinaryIO, TextIO, Union, cast
+from typing import BinaryIO, TextIO, cast
 
 import anyio
 from anyio import to_thread
@@ -137,7 +137,7 @@ async def create_windows_process(
     command: str,
     args: list[str],
     env: dict[str, str] | None = None,
-    errlog: Union[TextIO, int, None] = sys.stderr,
+    errlog: TextIO | int | None = sys.stderr,
     cwd: Path | str | None = None,
 ) -> Process | FallbackProcess:
     """Creates a subprocess in a Windows-compatible way with Job Object support.
@@ -196,7 +196,7 @@ async def _create_windows_fallback_process(
     command: str,
     args: list[str],
     env: dict[str, str] | None = None,
-    errlog: Union[TextIO, int, None] = sys.stderr,
+    errlog: TextIO | int | None = sys.stderr,
     cwd: Path | str | None = None,
 ) -> FallbackProcess:
     """Create a subprocess using subprocess.Popen as a fallback when anyio fails.

tests/client/test_stdio.py

@@ -740,6 +740,15 @@ def test_jupyter_detection_non_notebook_ipython(self):
             result = _is_jupyter_environment()
             assert result is False
 
+    def test_jupyter_detection_ipython_returns_none(self):
+        """Test that _is_jupyter_environment returns False when get_ipython() returns None."""
+        mock_ipython_module = MagicMock()
+        mock_ipython_module.get_ipython = MagicMock(return_value=None)
+
+        with patch.dict("sys.modules", {"IPython": mock_ipython_module}):
+            result = _is_jupyter_environment()
+            assert result is False
+
     @pytest.mark.anyio
     async def test_stderr_reader_jupyter_mode(self):
         """Test that stderr is captured and printed in Jupyter mode."""