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_cpu_wna16.py

@@ -0,0 +1,24 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+import pytest
+
+from vllm.platforms import current_platform
+
+if not current_platform.is_cpu():
+    pytest.skip("skipping CPU-only tests", allow_module_level=True)
+
+MODELS = [
+    "TheBloke/TinyLlama-1.1B-Chat-v1.0-AWQ",
+    "TheBloke/TinyLlama-1.1B-Chat-v1.0-GPTQ",  # with g_idx
+    "Qwen/Qwen1.5-0.5B-Chat-GPTQ-Int4",  # without g_idx
+]
+DTYPE = ["bfloat16"]
+
+
+@pytest.mark.parametrize("model", MODELS)
+@pytest.mark.parametrize("dtype", DTYPE)
+def test_cpu_quant(vllm_runner, model, dtype):
+    with vllm_runner(model, dtype=dtype) as llm:
+        output = llm.generate_greedy(["The capital of France is"], max_tokens=32)
+    assert output
+    print(output)