Product updates: Multi-node training clusters, B200 and H200s, and Client 1.0 release

Introduces multi-node training clusters via the `@clustered` decorator, enabling co-scheduled and co-located GPUs across multiple hosts with high-speed RDMA interconnect (3.2 Tbps Infiniband) for linear scaling. Highlights Quora's use of Modal sandboxes for Poe, achieving up to 1,000 Sandboxes per second and saving engineering time.