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/vllm/scripts.py

@@ -0,0 +1,17 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+from vllm.entrypoints.cli.main import main as vllm_main
+from vllm.logger import init_logger
+
+logger = init_logger(__name__)
+
+
+# Backwards compatibility for the move from vllm.scripts to
+# vllm.entrypoints.cli.main
+def main():
+    logger.warning(
+        "vllm.scripts.main() is deprecated. Please re-install "
+        "vllm or use vllm.entrypoints.cli.main.main() instead."
+    )
+    vllm_main()