fix: restore LD_PRELOAD libcccl_allocator.so — verified compiles in docker build

verify_submission.sh confirmed: CCCL preload compiles and loads on BI-V100.
Was removed in 8d2f30f0 due to crash concern, but the .so is built by
patch_ops.sh during docker build so it will always exist at runtime.

computility-run.yaml

@@ -49,4 +49,6 @@ env:
       value: '1'
     - name: PYTORCH_CUDA_ALLOC_CONF
       value: max_split_size_mb:512
+    - name: LD_PRELOAD
+      value: /workspace/qwen3_6_scripts/cccl_preload/libcccl_allocator.so