add release notes

Author: nammn

changelog/20250826_feature_migrate_agent_repo.md

@@ -0,0 +1,11 @@
+---
+title: migrate agent repo
+kind: feature
+date: 2025-08-26
+---
+
+* we've migrated the agents to a new repository: `quay.io/mongodb/mongodb-agent`.
+  * the agents in the new repository will support x86-64, ARM64, s390x, and ppc64le.
+  * operator running >=MCK1.3.0 and static cannot use the agents at `quay.io/mongodb/mongodb-agent-ubi`.
+* `quay.io/mongodb/mongodb-agent-ubi` should not be used anymore, it's only there for backwards compatibility.
+* More can be read in the [public docs](https://www.mongodb.com/docs/kubernetes/upcoming/tutorial/plan-k8s-op-compatibility/#supported-hardware-architectures)