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/tests/kernels/helion/test_utils.py

@@ -0,0 +1,32 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""Unit tests for Helion utility functions."""
+
+import pytest
+
+from vllm.kernels.helion.utils import canonicalize_gpu_name
+
+
+@pytest.mark.parametrize(
+    "driver_reported_name,expected",
+    [
+        ("NVIDIA H200", "nvidia_h200"),
+        ("NVIDIA A100-SXM4-80GB", "nvidia_a100"),
+        ("NVIDIA H100 80GB HBM3", "nvidia_h100"),
+        ("NVIDIA H100 PCIe", "nvidia_h100"),
+        ("NVIDIA H100 SXM5", "nvidia_h100"),
+        ("NVIDIA GeForce RTX 4090", "nvidia_geforce_rtx_4090"),
+        ("AMD Instinct MI300X", "amd_instinct_mi300x"),
+        ("Tesla V100-SXM2-32GB", "tesla_v100"),
+    ],
+)
+def test_canonicalize_gpu_name(driver_reported_name, expected):
+    """Test GPU name canonicalization."""
+    assert canonicalize_gpu_name(driver_reported_name) == expected
+
+
+@pytest.mark.parametrize("invalid_name", ["", "   ", "\t", "\n"])
+def test_canonicalize_gpu_name_rejects_empty(invalid_name):
+    """Test that empty or whitespace-only names are rejected."""
+    with pytest.raises(ValueError, match="cannot be empty"):
+        canonicalize_gpu_name(invalid_name)