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/src/components/form/formState.ts

@@ -2,10 +2,10 @@
 // filtering, the save payload, 422 detail mapping and focus.
 import type { AdminRecord, ErrorBody, FormField } from '../../api/types'
 import { permissionValues } from './control'
-import { localeRecord } from './mlLocale'
+import { isMLFieldType, localeRecord } from './mlLocale'
 import { isRegistered } from './registry'
 
-export { ML_LOCALE_CHANGE, broadcastMLLocale, localeRecord } from './mlLocale'
+export { ML_LOCALE_CHANGE, broadcastMLLocale, isMLFieldType, localeRecord } from './mlLocale'
 
 /** The screen a field is filtered for: the two form modes and the read-only preview (D-11). */
 export type FormMode = 'create' | 'update' | 'preview'
@@ -65,7 +65,7 @@ export function editablePayload(fields: FormField[], values: AdminRecord, mode:
       out[field.name] = permissionValues(field, value)
       continue
     }
-    if (field.type === 'mltext' || field.type === 'mlmarkdown') {
+    if (isMLFieldType(field.type)) {
       out[field.name] = localeRecord(value)
       continue
     }
@@ -111,10 +111,6 @@ export function changedLocales(previous: unknown, next: unknown): string[] {
  * whole field when no locale is given, one locale of an ML target otherwise. */
 export type PresetEdited = (target: string, locale?: string) => boolean
 
-function isMLType(type: string | undefined): boolean {
-  return type === 'mltext' || type === 'mlmarkdown'
-}
-
 /**
  * The preset targets of `source` (fields.yaml `preset`) to rewrite after the
  * source changed from `previous` to `next`: target name -> new value. Targets
@@ -140,7 +136,7 @@ export function presetUpdates(
   isEdited: PresetEdited,
 ): AdminRecord {
   const out: AdminRecord = {}
-  const sourceML = isMLType(fields.find((field) => field.name === source)?.type)
+  const sourceML = isMLFieldType(fields.find((field) => field.name === source)?.type)
   for (const field of fields) {
     const preset = field.preset
     if (!preset || preset.field !== source || (field.type !== 'text' && field.type !== 'mltext')) {
@@ -188,7 +184,7 @@ export function initialValues(fields: FormField[], enabledLocales: readonly stri
       out[field.name] = false
     } else if (field.type === 'relation' && field.multiple) {
       out[field.name] = []
-    } else if (field.type === 'mltext' || field.type === 'mlmarkdown') {
+    } else if (isMLFieldType(field.type)) {
       const seed: Record<string, string> = {}
       for (const code of enabledLocales) {
         seed[code] = ''