docs: add Kontext try-it link

README.md

@@ -56,6 +56,12 @@ context. It does not infer intent or make a complete authorization decision.
 It is intended as one signal layered underneath deterministic protections and
 runtime authorization policy, not as the sole control for executing commands.
 
+## Try it
+
+Kestrel is available as part of Kontext, where it evaluates the cyber risk of
+agent tool calls locally. Learn more and try it at
+[kontext.security](https://kontext.security).
+
 ## Integrity
 
 ```text