Fill in the 9 settings.directoryPicker.* creation keys in all 9 locales,
reusing the sidebar's existing folder vocabulary so the two folder-creation
surfaces stay consistent:
- newFolder matches sidebar.createFolder, nameInvalid matches
sidebar.dragDrop.invalidFolderName, createError is
sidebar.createFolderResult.failed without its {message} suffix, and
alreadyExists drops the "here" of sidebar.renameFolderResult.targetExists.
- German keeps the formal register, Spanish the tú form.
- Document the renderings in the i18n guidelines (§2) and record the feature
in the status block.
No [TODO: Translate] placeholder remains in any locale.