fix: update banner URL to canonical ArtemisAI/pi-mem

Author: ArtemisAI

pi-agent/README.md

@@ -1,7 +1,7 @@
 # pi-agent-memory
 
 <p align="center">
-  <img src="https://raw.githubusercontent.com/ArtemisAI/claude-mem/main/pi-agent/banner.png" alt="Pi-agent-memory banner" width="600">
+  <img src="https://raw.githubusercontent.com/ArtemisAI/pi-mem/main/pi-agent/banner.png" alt="Pi-agent-memory banner" width="600">
 </p>
 
 <p align="center">