Add PyG packages to torch backend (#15911)

## Summary

These are now supported on pyx.

Author: charliermarsh

crates/uv-torch/src/backend.rs

@@ -322,11 +322,16 @@ impl TorchStrategy {
             TorchSource::Pyx => {
                 matches!(
                     package_name.as_str(),
-                    "flash-attn"
+                    "deepspeed"
+                        | "flash-attn"
                         | "flash-attn-3"
                         | "megablocks"
                         | "natten"
-                        | "deepspeed"
+                        | "pyg-lib"
+                        | "torch-cluster"
+                        | "torch-scatter"
+                        | "torch-sparse"
+                        | "torch-spline-conv"
                         | "vllm"
                         | "torch"
                         | "torch-model-archiver"