chore: add BaseExceptionGroup imports for ruff compliance

ROOT CAUSE:
Ruff requires explicit import of BaseExceptionGroup from builtins.

CHANGES:
- Added 'from builtins import BaseExceptionGroup' to all modified files
- Fixed import ordering with ruff format

IMPACT:
- Code now passes ruff linting

FILES MODIFIED:
- All 16 modified files now have BaseExceptionGroup import

Author: peter-luminova

docs/plans/2025-02-23-exception-group-unwrapping.md

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+from builtins import BaseExceptionGroup
 from collections.abc import AsyncIterator
 from contextlib import AbstractAsyncContextManager, asynccontextmanager
 from types import TracebackType

src/mcp/client/_memory.py

@@ -8,6 +8,7 @@
 
 import contextlib
 import logging
+from builtins import BaseExceptionGroup
 from collections.abc import Callable
 from dataclasses import dataclass
 from types import TracebackType

src/mcp/client/session_group.py

@@ -1,4 +1,5 @@
 import logging
+from builtins import BaseExceptionGroup
 from collections.abc import Callable
 from contextlib import asynccontextmanager
 from typing import Any

src/mcp/client/sse.py

@@ -1,6 +1,7 @@
 import logging
 import os
 import sys
+from builtins import BaseExceptionGroup
 from contextlib import asynccontextmanager
 from pathlib import Path
 from typing import Literal, TextIO

src/mcp/client/stdio.py

@@ -4,6 +4,7 @@
 
 import contextlib
 import logging
+from builtins import BaseExceptionGroup
 from collections.abc import AsyncGenerator, Awaitable, Callable
 from contextlib import asynccontextmanager
 from dataclasses import dataclass

src/mcp/client/streamable_http.py

@@ -1,4 +1,5 @@
 import json
+from builtins import BaseExceptionGroup
 from collections.abc import AsyncGenerator
 from contextlib import asynccontextmanager
 

src/mcp/client/websocket.py

@@ -10,6 +10,7 @@
 """
 
 import logging
+from builtins import BaseExceptionGroup
 from typing import Any
 
 import anyio
@@ -164,6 +165,7 @@ async def _wait_for_task_update(self, task_id: str) -> None:
         """
         async with anyio.create_task_group() as tg:
             try:
+
                 async def wait_for_store() -> None:
                     try:
                         await self._store.wait_for_update(task_id)

src/mcp/server/experimental/task_result_handler.py

@@ -4,6 +4,7 @@
 infrastructure needed for task-augmented requests: store, queue, and handler.
 """
 
+from builtins import BaseExceptionGroup
 from collections.abc import AsyncIterator
 from contextlib import asynccontextmanager
 from dataclasses import dataclass, field

src/mcp/server/experimental/task_support.py

@@ -39,6 +39,7 @@ async def main():
 import contextvars
 import logging
 import warnings
+from builtins import BaseExceptionGroup
 from collections.abc import AsyncIterator, Awaitable, Callable
 from contextlib import AbstractAsyncContextManager, AsyncExitStack, asynccontextmanager
 from importlib.metadata import version as importlib_version