chore: import upstream snapshot with attribution

tests/shared/test_context_streams.py

@@ -0,0 +1,20 @@
+"""Tests for the contextvars-carrying memory-stream wrappers."""
+
+import anyio
+import pytest
+
+from mcp.shared._context_streams import create_context_streams
+
+pytestmark = pytest.mark.anyio
+
+
+async def test_sync_close_closes_the_underlying_streams() -> None:
+    """The wrappers mirror anyio's memory streams: close() is the sync form of aclose()."""
+    send, receive = create_context_streams[str](1)
+    await send.send("queued")
+    send.close()
+    receive.close()
+    with pytest.raises(anyio.ClosedResourceError):
+        await send.send("after close")
+    with pytest.raises(anyio.ClosedResourceError):
+        await receive.receive()