feat(14.2.1-06): hydrate relation-child update and show ML maps

UpdateChild and ShowChild now lift, apply, and hydrate nested locales the same way as host CRUD, so a child form keeps English on the column and Polish through the writer.

Co-authored-by: Cursor <cursoragent@cursor.com>

modules/cabana/relation_child_ml_test.go

@@ -180,6 +180,36 @@ func TestRelationChildMLNestedSave(t *testing.T) {
 		t.Fatalf("Polish attributes = %#v", writer.attrs)
 	}
 
+	updated, err := svc.UpdateChild(context.Background(), cc, "entries", parent.ID, row.ID, RecordInput{Body: map[string]any{
+		"title": map[string]any{"en": "Hello", "pl": "Cześć"},
+	}})
+	if err != nil {
+		t.Fatalf("update: %v", err)
+	}
+	got, ok = updated.Data["title"].(map[string]string)
+	wantUpdated := map[string]string{"en": "Hello", "pl": "Cześć"}
+	if !ok || !reflect.DeepEqual(got, wantUpdated) {
+		t.Fatalf("update title = %#v", updated.Data["title"])
+	}
+	if err := db.First(&row, row.ID).Error; err != nil {
+		t.Fatal(err)
+	}
+	if row.Title != "Hello" {
+		t.Fatalf("host title after update = %q", row.Title)
+	}
+	if writer.attrs["pl"]["title"] != "Cześć" {
+		t.Fatalf("updated Polish attributes = %#v", writer.attrs)
+	}
+
+	shown, err := svc.ShowChild(context.Background(), cc, "entries", parent.ID, row.ID)
+	if err != nil {
+		t.Fatalf("show: %v", err)
+	}
+	got, ok = shown.Data["title"].(map[string]string)
+	if !ok || !reflect.DeepEqual(got, wantUpdated) {
+		t.Fatalf("show title = %#v", shown.Data["title"])
+	}
+
 	before := int64(0)
 	if err := db.Model(&mlEntry{}).Count(&before).Error; err != nil {
 		t.Fatal(err)