chore: add server-changes for pr04

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: d-cs

.server-changes/run-engine-store-routing-seam.md

@@ -0,0 +1,6 @@
+---
+area: webapp
+type: feature
+---
+
+Route run engine lifecycle operations through the run store and a control-plane resolver so run data can live on a dedicated backing store separate from the control plane.