chore: update .gitignore and add AGENT.md file

- Remove AGENT.md from .gitignore to track it in the repository.
- Create a new AGENT.md file in the src/stories directory.

Author: ssdeanx

.gitignore

@@ -234,4 +234,4 @@ src/mastra/public/workspace/tbc-shaman.md
 
 *storybook.log
 storybook-static
-src/stories/AGENT.md
+