test: add comprehensive tests for Jupyter stderr support

- Test Jupyter environment detection (with/without IPython)
- Test stderr printing in Jupyter and non-Jupyter environments
- Test IPython display fallback when display fails
- Test stderr capture and piping
- Test stderr reader exception handling
- Test empty line filtering and final buffer handling
- Test process without stderr stream

Achieves 100% code coverage for the new functionality.

Author: dgenio

src/mcp/client/stdio/__init__.py

@@ -60,7 +60,7 @@ def _is_jupyter_notebook() -> bool:
         from IPython import get_ipython  # type: ignore[import-not-found]
 
         ipython = get_ipython()  # type: ignore[no-untyped-call]
-        return ipython is not None and ipython.__class__.__name__ in ("ZMQInteractiveShell", "TerminalInteractiveShell")
+        return ipython is not None and ipython.__class__.__name__ in ("ZMQInteractiveShell", "TerminalInteractiveShell")  # type: ignore[union-attr]
     except ImportError:
         return False