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/examples/online_serving/sagemaker-entrypoint.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+
+# Define the prefix for environment variables to look for
+PREFIX="SM_VLLM_"
+ARG_PREFIX="--"
+
+# Initialize an array for storing the arguments
+# port 8080 required by sagemaker, https://docs.aws.amazon.com/sagemaker/latest/dg/your-algorithms-inference-code.html#your-algorithms-inference-code-container-response
+ARGS=(--port 8080)
+
+# Loop through all environment variables
+while IFS='=' read -r key value; do
+    # Remove the prefix from the key, convert to lowercase, and replace underscores with dashes
+    arg_name=$(echo "${key#"${PREFIX}"}" | tr '[:upper:]' '[:lower:]' | tr '_' '-')
+
+    # Add the argument name and value to the ARGS array
+    ARGS+=("${ARG_PREFIX}${arg_name}")
+    if [ -n "$value" ]; then
+        ARGS+=("$value")
+    fi
+done < <(env | grep "^${PREFIX}")
+
+# Pass the collected arguments to the main entrypoint
+exec standard-supervisor vllm serve "${ARGS[@]}"