test/s3vectors: wait for the S3 port before handing out the cluster (#12383)

The fixture waited for the Lance catalog port and the engine, but weed s3
opens its HTTP port last, about half a second after the catalog here. The
open cluster's engine now registers within that window, so
test_engine_without_credentials met a connection refused on the go and rust
single legs. Wait for the S3 port like the other listeners.


Claude-Session: https://claude.ai/code/session_011UpvafvK8JpagF94MHWqwK

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

test/s3vectors/conftest.py

@@ -297,6 +297,7 @@ def run_cluster(param, tmp_path_factory, identities):
                      "-ip=127.0.0.1", "-ip.bind=127.0.0.1", f"-port={s3}",
                      f"-port.grpc={s3_grpc}", "-port.iceberg=0", f"-port.lance={lance}"], unset)
         wait_for(lambda: http_ready(f"http://127.0.0.1:{lance}/v1/namespace/root/list"), processes, "catalog not ready")
+        wait_for(lambda: listening(s3), processes, "s3 not ready")
         if os.environ.get("VECTOR_TLS") or read_jwt_key or encrypt:
             probe_hardening(endpoint, filer, vol, directory, read_jwt_key)
         start("vector", [engine, "--namespace", f"http://127.0.0.1:{lance}",