Fix cross-loop test: compare transport identity, not id()

After close(), Python can reuse the freed memory address for the next
transport, making id() values match across separate asyncio.run()
calls. Keep the first transport reference alive and use `is not`
instead.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: jrvb-rl

tests/test_shared_pool.py

@@ -292,16 +292,16 @@ class TestAsyncCrossLoop:
     def test_separate_loops_get_separate_transports(self):
         """Clients created in different asyncio.run() calls must not share a transport."""
 
-        async def create_client() -> int:
+        async def create_client() -> Any:
             c = _make_async_client(shared_http_pool=True)
-            transport_id = id(_get_transport(c))
+            transport = _get_transport(c)
             await c.close()
-            return transport_id
+            return transport
 
-        id1 = asyncio.run(create_client())
-        id2 = asyncio.run(create_client())
+        t1 = asyncio.run(create_client())
+        t2 = asyncio.run(create_client())
 
-        assert id1 != id2, "each loop should get its own transport"
+        assert t1 is not t2, "each loop should get its own transport"
 
     def test_same_loop_shares_transport(self):
         """Clients created in the same asyncio.run() must share a transport."""