Add Unity non-blocking runtime diagram

Add the game-engine/model timing diagram near the top of the model card and summarize how Causal GPT-RL removes inference from the engine's critical path.

README.md

@@ -40,6 +40,12 @@ environment folder ships the original `config.json` + `model.safetensors`, so a
 policy can be loaded directly and re-evaluated while retaining a different amount
 of history, plus the ONNX variants used for Unity deployment.
 
+![The game engine does not wait for the model](assets/game-engine-does-not-wait-for-the-model.svg)
+
+**Causal GPT-RL generates the next action from the completed trajectory while
+the game engine advances the world, removing model inference from the engine's
+critical path.**
+
 - **Code (GitHub):** [ccnets-team/causal-gpt-rl](https://github.com/ccnets-team/causal-gpt-rl)
 - **Hugging Face org:** https://huggingface.co/ccnets
 - Website: https://ccnets.org