- enabledContentLocales moves TranslationWriter.DefaultLocale to index 0
and keeps the other enabled codes in the writer's order
- every ML control opens on enabledLocales[0], so the form now shows the
host-column values (content, excerpt, title, slug) instead of an empty
non-default locale
- a DefaultLocale error is logged and keeps the writer's order
- README and forms docs: default locale first