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/basic/offline_inference/README.md

@@ -0,0 +1,73 @@
+# Offline Inference
+
+The `LLM` class provides the primary Python interface for doing offline inference, which is interacting with a model without using a separate model inference server.
+
+## Usage
+
+The first script in this example shows the most basic usage of vLLM. If you are new to Python and vLLM, you should start here.
+
+```bash
+python examples/basic/offline_inference/basic.py
+```
+
+The rest of the scripts include an [argument parser](https://docs.python.org/3/library/argparse.html), which you can use to pass any arguments that are compatible with [`LLM`](https://docs.vllm.ai/en/latest/api/offline_inference/llm.html). Try running the script with `--help` for a list of all available arguments.
+
+```bash
+python examples/basic/offline_inference/classify.py
+```
+
+```bash
+python examples/basic/offline_inference/embed.py
+```
+
+```bash
+python examples/basic/offline_inference/score.py
+```
+
+The chat and generate scripts also accept the [sampling parameters](https://docs.vllm.ai/en/latest/api/inference_params.html#sampling-parameters): `max_tokens`, `temperature`, `top_p` and `top_k`.
+
+```bash
+python examples/basic/offline_inference/chat.py
+```
+
+```bash
+python examples/basic/offline_inference/generate.py
+```
+
+## Features
+
+In the scripts that support passing arguments, you can experiment with the following features.
+
+### Default generation config
+
+The `--generation-config` argument specifies where the generation config will be loaded from when calling `LLM.get_default_sampling_params()`. If set to ‘auto’, the generation config will be loaded from model path. If set to a folder path, the generation config will be loaded from the specified folder path. If it is not provided, vLLM defaults will be used.
+
+> If max_new_tokens is specified in generation config, then it sets a server-wide limit on the number of output tokens for all requests.
+
+Try it yourself with the following argument:
+
+```bash
+--generation-config auto
+```
+
+### Quantization
+
+#### GGUF
+
+vLLM supports models that are quantized using GGUF.
+
+Try one yourself using the `repo_id:quant_type` format to load directly from HuggingFace:
+
+```bash
+--model unsloth/Qwen3-0.6B-GGUF:Q4_K_M --tokenizer Qwen/Qwen3-0.6B
+```
+
+### CPU offload
+
+The `--cpu-offload-gb` argument can be seen as a virtual way to increase the GPU memory size. For example, if you have one 24 GB GPU and set this to 10, virtually you can think of it as a 34 GB GPU. Then you can load a 13B model with BF16 weight, which requires at least 26GB GPU memory. Note that this requires fast CPU-GPU interconnect, as part of the model is loaded from CPU memory to GPU memory on the fly in each model forward pass.
+
+Try it yourself with the following arguments:
+
+```bash
+--model meta-llama/Llama-2-13b-chat-hf --cpu-offload-gb 10
+```