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/features/speculative_decoding/eagle.md

@@ -0,0 +1,67 @@
+# EAGLE Draft Models
+
+The following code configures vLLM to use speculative decoding where proposals are generated by an [EAGLE (Extrapolation Algorithm for Greater Language-model Efficiency)](https://arxiv.org/pdf/2401.15077) based draft model. A more detailed example for offline mode, including how to extract request level acceptance rate, can be found in [examples/offline_inference/spec_decode.py](../../../examples/offline_inference/spec_decode.py)
+
+## Eagle Drafter Example
+
+```python
+from vllm import LLM, SamplingParams
+
+prompts = ["The future of AI is"]
+sampling_params = SamplingParams(temperature=0.8, top_p=0.95)
+
+llm = LLM(
+    model="meta-llama/Meta-Llama-3-8B-Instruct",
+    tensor_parallel_size=4,
+    speculative_config={
+        "model": "yuhuili/EAGLE-LLaMA3-Instruct-8B",
+        "draft_tensor_parallel_size": 1,
+        "num_speculative_tokens": 2,
+        "method": "eagle",
+    },
+)
+
+outputs = llm.generate(prompts, sampling_params)
+
+for output in outputs:
+    prompt = output.prompt
+    generated_text = output.outputs[0].text
+    print(f"Prompt: {prompt!r}, Generated text: {generated_text!r}")
+```
+
+## Eagle3 Drafter Example
+
+```python
+from vllm import LLM, SamplingParams
+
+prompts = ["The future of AI is"]
+sampling_params = SamplingParams(temperature=0.8, top_p=0.95)
+
+llm = LLM(
+    model="meta-llama/Meta-Llama-3-8B-Instruct",
+    tensor_parallel_size=2,
+    speculative_config={
+        "model": "RedHatAI/Llama-3.1-8B-Instruct-speculator.eagle3",
+        "draft_tensor_parallel_size": 2,
+        "num_speculative_tokens": 2,
+        "method": "eagle3",
+    },
+)
+
+outputs = llm.generate(prompts, sampling_params)
+
+for output in outputs:
+    prompt = output.prompt
+    generated_text = output.outputs[0].text
+    print(f"Prompt: {prompt!r}, Generated text: {generated_text!r}")
+```
+
+## Pre-Trained Eagle Draft Models
+
+A variety of EAGLE draft models are available on the Hugging Face hub:
+
+* [RedHatAI/speculator-models](https://huggingface.co/collections/RedHatAI/speculator-models)
+* [yuhuili/models](https://huggingface.co/yuhuili/models?search=eagle)
+
+!!! warning
+    If you are using `vllm<0.7.0`, please use [this script](https://gist.github.com/abhigoyal1997/1e7a4109ccb7704fbc67f625e86b2d6d) to convert the speculative model and specify `"model": "path/to/modified/eagle/model"` in `speculative_config`.