Filter known anyio stream teardown warnings in streamable HTTP security tests

The three tests that complete the initialize handshake leak anyio memory
streams at transport teardown when run in process. The scoped filters in
tests/interaction/conftest.py cover full-suite runs, but they only load
when that package is collected, so a targeted run of this file alone
turns the ResourceWarning into a failure under filterwarnings=error.
Mirror the module-level filterwarnings marks already used in
tests/shared/test_sse.py.

Author: maxisbey

tests/server/test_streamable_http_security.py

@@ -19,6 +19,21 @@
 # Host header is a localhost form; nothing listens here.
 BASE_URL = "http://127.0.0.1:8000"
 
+# v1's streamable-HTTP server transport leaks a handful of anyio memory streams on teardown when
+# run in process; the old subprocess harness never observed them. The interaction suite registers
+# the same two scoped filters globally from tests/interaction/conftest.py (see the comment there),
+# but they only take effect when that package's conftest is loaded; these markers keep the tests
+# that complete the initialize handshake passing in isolated runs. Markers are item-scoped, so
+# they cannot cover the GC flush at session cleanup: an isolated run without xdist (`-n 0`) still
+# exits nonzero after all tests pass. The default xdist runs (addopts has `-n auto`) are
+# unaffected, as are full-suite runs, where the interaction conftest's ini-level filters apply.
+# The filters are scoped to anyio's MemoryObject*Stream leak signature so an unrelated leak
+# still fails the suite.
+pytestmark = [
+    pytest.mark.filterwarnings("ignore:.*MemoryObject(Send|Receive)Stream:pytest.PytestUnraisableExceptionWarning"),
+    pytest.mark.filterwarnings("ignore:.*MemoryObject(Send|Receive)Stream:ResourceWarning"),
+]
+
 
 @asynccontextmanager
 async def streamable_http_security_client(