fix: revert clusterGroupName to simple for main branch merge

The clusterGroupName was changed to 'baremetal' in commit a601af0 for
deployment testing. Reverting to 'simple' as the default so existing
users are not affected when this PR merges to main.

The baremetal clusterGroup remains available by setting
clusterGroupName: baremetal in user overrides or CI.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: butler54

values-global.yaml

@@ -26,7 +26,7 @@ main:
   # WARNING
   # This default configuration uses a single cluster on azure.
   # It fundamentally violates the separation of duties.
-  clusterGroupName: baremetal
+  clusterGroupName: simple
   multiSourceConfig:
     enabled: true
     clusterGroupChartVersion: 0.9.*