[BLOG] <Introducing OpenSearch Relevance Agent>

### Describe the blog post

We are introducing Agentic Relevance tuning feature in 3.6. This is a blog plot introducing this feature. 

### Expected Title

OpenSearch

### Authors Name

Bobby Mohammed, Daniel Wrigley

### Authors Email

bobbyaws@amazon.com

### Target Draft Date

4/6/26

### Blog Post Category

technical

### Target Publication Date

4/6/26

### Additional Info

_No response_