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/docs/deployment/integrations/kaito.md

@@ -0,0 +1,5 @@
+# KAITO
+
+[KAITO](https://kaito-project.github.io/kaito/docs/) is a Kubernetes operator that supports deploying and serving LLMs with vLLM. It offers managing large models via container images with built-in OpenAI-compatible inference, auto-provisioning GPU nodes and curated model presets.
+
+Please refer to [quick start](https://kaito-project.github.io/kaito/docs/quick-start) for more details.