Area 4 (join 11): the Go build module lists its kept builds through buildstep's bus-free judgement

buildstep no longer takes mesh-sdk's buscalls objects (that package now reaches
the bus): the module judges each object of its kept-builds store with
KeptBuildOf and orders them with SortKept.

Builds: design 47 G (join 11 area 4: buildstep kept free of the bus)

Claude-Session: https://claude.ai/code/session_01NcbgfGKaxw984XyAPfLm4h

modules/mesh-build-go/cmd/mesh-build-go/keptbuilds.go

@@ -64,7 +64,17 @@ func (m *Module) keptBuilds() ([]KeptBuild, error) {
 	if err != nil {
 		return nil, err
 	}
-	return sdkstep.KeptBuildsOf(infos, m.Node), nil
+	out := []KeptBuild{}
+	for _, i := range infos {
+		if i.Deleted {
+			continue
+		}
+		if k, ok := sdkstep.KeptBuildOf(i.Name, i.Description, i.Size, i.Modified, m.Node); ok {
+			out = append(out, k)
+		}
+	}
+	sdkstep.SortKept(out)
+	return out, nil
 }
 
 // dropKeptBuild removes the kept build of the hex digest this node keeps; one it does not keep is no error.