Fix scheduling metadata to use loaded headers

When templates are loaded via GetTemplate, the memfileHeader and rootfsHeader
SetOnce fields were initialized with nil values. Although Fetch() would load
the actual headers from storage via NewStorage(), these loaded headers were
never propagated back to the SetOnce fields. This caused SchedulingMetadata()
to always return nil for templates loaded through the normal path.

The fix updates the SetOnce fields with the loaded headers from the Storage
objects after they are successfully created, but only when the initial header
was nil.

Author: cursoragent

packages/orchestrator/pkg/sandbox/template/storage_template.go

@@ -206,6 +206,12 @@ func (t *storageTemplate) Fetch(ctx context.Context, buildStore *build.DiffStore
 			return nil
 		}
 
+		if memHdr == nil {
+			if err := t.memfileHeader.SetValue(memfileStorage.Header()); err != nil {
+				return fmt.Errorf("failed to update memfile header: %w", err)
+			}
+		}
+
 		if err := t.memfile.SetValue(memfileStorage); err != nil {
 			return fmt.Errorf("failed to set memfile value: %w", err)
 		}
@@ -243,6 +249,12 @@ func (t *storageTemplate) Fetch(ctx context.Context, buildStore *build.DiffStore
 			return nil
 		}
 
+		if rootHdr == nil {
+			if err := t.rootfsHeader.SetValue(rootfsStorage.Header()); err != nil {
+				return fmt.Errorf("failed to update rootfs header: %w", err)
+			}
+		}
+
 		if err := t.rootfs.SetValue(rootfsStorage); err != nil {
 			return fmt.Errorf("failed to set rootfs value: %w", err)
 		}