feat(admin): render mltextarea fields per locale

- MLField.vue is the one locale-switching wrapper; MLTextField,
  MLMarkdownField and the new MLTextareaField are shells around it
- isMLFieldType replaces the inline ML type-name checks in formState,
  FormView and RelationChildModal
- register mltextarea as a group-labelled control; rebuild dist

admin/tests/form/registry.test.ts

@@ -9,6 +9,7 @@ import TextareaField from '../../src/components/form/fields/TextareaField.vue'
 import PartialField from '../../src/components/form/fields/PartialField.vue'
 import MarkdownField from '../../src/components/form/fields/MarkdownField.vue'
 import MLMarkdownField from '../../src/components/form/fields/MLMarkdownField.vue'
+import MLTextareaField from '../../src/components/form/fields/MLTextareaField.vue'
 import MLTextField from '../../src/components/form/fields/MLTextField.vue'
 import PasswordField from '../../src/components/form/fields/PasswordField.vue'
 import PermissionEditorField from '../../src/components/form/fields/PermissionEditorField.vue'
@@ -203,7 +204,15 @@ describe('markdown and multilingual field types (Phase 14.2.1)', () => {
     expect(groupLabelled('mlmarkdown')).toBe(true)
   })
 
-  it.each(['mlunknown', 'MLTEXT', 'richtext', 'markdowneditor'])(
+  it('registers mltextarea as an editable group-labelled type', () => {
+    expect(rendererFor('mltextarea')).toBe(MLTextareaField)
+    expect(isRegistered('mltextarea')).toBe(true)
+    expect(needsRecord('mltextarea')).toBe(false)
+    expect(ownsLabel('mltextarea')).toBe(false)
+    expect(groupLabelled('mltextarea')).toBe(true)
+  })
+
+  it.each(['mlunknown', 'MLTEXT', 'MLTEXTAREA', 'richtext', 'markdowneditor'])(
     'falls back to UnsupportedField for unknown ML type %j',
     (type) => {
       expect(isRegistered(type)).toBe(false)