Add supermodeltools.com/trial CTA (#12)

* docs: add supermodeltools.com/trial CTA

* docs: punch up /trial CTA with 40%+ token-savings hook

Author: jonathanpopham

README.md

@@ -16,7 +16,7 @@ If this is useful, please star our tools — it helps us grow:
 
 ### 1. Get an API key
 
-Sign up at [dashboard.supermodeltools.com](https://dashboard.supermodeltools.com) and create an API key.
+**Save 40%+ on agent token costs — start free → [supermodeltools.com/trial](https://supermodeltools.com/trial)**
 
 ### 2. Add the secret to your repository