docs: add Signal-Decision Architecture blog to README news

Add the latest blog post about Signal-Decision Driven Architecture
to the Latest News section in README.md.

Blog: https://blog.vllm.ai/2025/11/19/signal-decision.html
Signed-off-by: bitliu <[email protected]>

Author: Xunzhuo

README.md

@@ -17,6 +17,7 @@
 
 *Latest News* 🔥
 
+- [2025/11/19] We released the [Signal-Decision Driven Architecture: Reshaping Semantic Routing at Scale](https://blog.vllm.ai/2025/11/19/signal-decision.html) 🧠
 - [2025/11/03] **Our paper** [Category-Aware Semantic Caching for Heterogeneous LLM Workloads](https://arxiv.org/abs/2510.26835) published 📝
 - [2025/10/26] We reached 2000 stars on GitHub! 🔥
 - [2025/10/21] We announced the [2025 Q4 Roadmap: Journey to Iris](https://vllm-semantic-router.com/blog/q4-roadmap-iris) 📅.