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/prometheus_grafana/docker-compose.yaml

@@ -0,0 +1,19 @@
+# docker-compose.yaml
+version: "3"
+
+services:
+  prometheus:
+    image: prom/prometheus:latest
+    extra_hosts:
+      - "host.docker.internal:host-gateway"     # allow a direct connection from container to the local machine
+    ports:
+      - "9090:9090"   # the default port used by Prometheus
+    volumes:
+      - ${PWD}/prometheus.yaml:/etc/prometheus/prometheus.yml # mount Prometheus config file
+
+  grafana:
+    image: grafana/grafana:latest
+    depends_on:
+      - prometheus
+    ports:
+      - "3000:3000" # the default port used by Grafana