Faster Tensor Viewer

The tensor viewer now loads much faster on large sharded models. When you open a model's model.safetensors.index.json, the Hub sends the headers of all shards in a single request, so your browser no longer fetches each shard one by one. For example, DeepSeek-V3.2 now loads in 0.45s instead of 9.2s, GLM-5.3 in 0.57s instead of 4.0s, and Qwen2.5-72B-Instruct in 0.27s instead of 1.2s.