Add comment explaining filterwarnings on OTel test

Author: Kludex

tests/shared/test_otel.py

@@ -9,6 +9,8 @@
 pytestmark = pytest.mark.anyio
 
 
+# Logfire warns about propagated trace context by default (distributed_tracing=None).
+# This is expected here since we're testing cross-boundary context propagation.
 @pytest.mark.filterwarnings("ignore::RuntimeWarning")
 async def test_client_and_server_spans(capfire: CaptureLogfire):
     """Verify that calling a tool produces client and server spans with correct attributes."""