test: gh-106749 heal in StreamingASGITransport.__aexit__

The in-process ASGI bridge (tests/interaction/transports/_bridge.py)
cancels its task group on close. After main's #2764-2767 moved the
shared SHTTP/SSE/security tests to this transport, this became the
remaining unhealed throw site on 3.11. Same checkpoint pattern,
applied at the actual cancel site (_bridge.py is a helper, not a
snapshot test).

Author: maxisbey

tests/interaction/transports/_bridge.py

@@ -31,6 +31,7 @@
 
 import anyio
 import anyio.abc
+import anyio.lowlevel
 import httpx
 from anyio.streams.memory import MemoryObjectReceiveStream
 from starlette.types import ASGIApp, Message, Scope
@@ -88,6 +89,10 @@ async def __aexit__(
         if self._cancel_on_close:
             self._task_group.cancel_scope.cancel()
         await self._task_group.__aexit__(exc_type, exc_value, traceback)
+        # gh-106749: the cancel above is delivered via coro.throw() on
+        # CPython 3.11; resume via .send() so coverage's CTracer re-syncs
+        # for whatever the caller does after this context manager exits.
+        await anyio.lowlevel.cancel_shielded_checkpoint()
 
     async def handle_async_request(self, request: httpx.Request) -> httpx.Response:
         assert isinstance(request.stream, httpx.AsyncByteStream)