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/quantization/test_auto_round.py

@@ -0,0 +1,32 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""Test model set-up and inference for quantized HF models supported
+on the AutoRound.
+
+Validating the configuration and printing results for manual checking.
+
+Run `pytest tests/quantization/test_auto_round.py`.
+"""
+
+import pytest
+
+from vllm.platforms import current_platform
+
+MODELS = [
+    "OPEA/Qwen2.5-0.5B-Instruct-int4-sym-inc",  ##auto_round:auto_gptq
+    "Intel/Qwen2-0.5B-Instruct-int4-sym-AutoRound",  ##auto_round:auto_awq
+]
+
+
+@pytest.mark.skipif(
+    not current_platform.is_cpu()
+    and not current_platform.is_xpu()
+    and not current_platform.is_cuda(),
+    reason="only supports CPU/XPU/CUDA backend.",
+)
+@pytest.mark.parametrize("model", MODELS)
+def test_auto_round(vllm_runner, model):
+    with vllm_runner(model, enforce_eager=True) as llm:
+        output = llm.generate_greedy(["The capital of France is"], max_tokens=8)
+    assert output
+    print(f"{output[0][1]}")