Add vLLM v0.18.1 source tree with KV transfer abort fix

third_party/vllm/ now tracked in git for direct patch management.
Based on vLLM v0.18.1 release with one patch applied:

  vllm/v1/core/sched/scheduler.py:
    Replace fatal assert with graceful skip when KV transfer callback
    arrives for an already-aborted request during PD disaggregated serving.

Future vLLM modifications should be made directly in third_party/vllm/
and committed normally. The patches/ directory is kept as documentation
of what changed from upstream.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

third_party/vllm/.buildkite/scripts/hardware_ci/run-gh200-test.sh

@@ -0,0 +1,29 @@
+#!/bin/bash
+
+# This script build the GH200 docker image and run the offline inference inside the container.
+# It serves a sanity check for compilation and basic model usage.
+set -ex
+
+# Skip the new torch installation during build since we are using the specified version for arm64 in the Dockerfile
+python3 use_existing_torch.py
+
+# Try building the docker image
+DOCKER_BUILDKIT=1 docker build . \
+  --file docker/Dockerfile \
+  --target vllm-openai \
+  --platform "linux/arm64" \
+  -t gh200-test \
+  --build-arg max_jobs=66 \
+  --build-arg nvcc_threads=2 \
+  --build-arg RUN_WHEEL_CHECK=false \
+  --build-arg torch_cuda_arch_list="9.0+PTX"
+
+# Setup cleanup
+remove_docker_container() { docker rm -f gh200-test || true; }
+trap remove_docker_container EXIT
+remove_docker_container
+
+# Run the image and test offline inference
+docker run -e HF_TOKEN -e VLLM_WORKER_MULTIPROC_METHOD=spawn -v /root/.cache/huggingface:/root/.cache/huggingface --name gh200-test --gpus=all --entrypoint="" gh200-test bash -c '
+    python3 examples/basic/offline_inference/generate.py --model meta-llama/Llama-3.2-1B
+'