fix: add type ignore comments for pyright strict mode

ROOT CAUSE:
Pyright strict mode reports partially unknown types when
iterating over BaseExceptionGroup.exceptions tuple

CHANGES:
- Added type: ignore[reportUnknownVariableType] to for loop line
- Fixed location of type ignore comment to be on line with error

IMPACT:
CI pyright checks will now pass

FILES MODIFIED:
- src/mcp/shared/exceptions.py

Author: peter-luminova

src/mcp/shared/exceptions.py

@@ -143,7 +143,7 @@ def unwrap_task_group_exception(exc: BaseException) -> BaseException:
 
     # Find the first non-cancelled exception
     cancelled_exc_class = anyio.get_cancelled_exc_class()
-    for sub_exc in exc.exceptions:
+    for sub_exc in exc.exceptions:  # type: ignore[reportUnknownVariableType]
         if not isinstance(sub_exc, cancelled_exc_class):
             # Type narrowing: we know this is not a CancelledError
             return sub_exc  # type: ignore[reportUnknownVariableType]