feat(17-02): repeater field and dependent dropdown states

- RepeaterField: rows with drag handle, index, titleFrom title, error chip,
  move up/down (buttons, ArrowUp/ArrowDown on the handle, native drag and
  drop), expand/collapse, remove (asks only for a row holding a value),
  add with nested defaults, maxItems counter, empty state, collapse all;
  every change edits form state only
- 422 row paths (content.3.answer) open the row, mark it and focus the
  nested control; the banner no longer repeats row messages
- DropdownField dependsOn: waiting, loading, not used, empty, loaded with
  depth indent, failed with retry; cached per sibling value, last request
  wins, a stale value is cleared after a sibling change and announced
- FormView provides form feedback (errors and notices by row path, the
  polite live region, its confirm dialog) and the options cache; FormGrid
  provides the sibling scope for repeater rows
- repeater.* and form.dependent_* phrase keys (en, pl), smoke specs, docs

admin/src/views/FormView.vue

@@ -13,7 +13,18 @@ import { mapWinterUrl } from '../app/winterUrl'
 import FormErrorBanner from '../components/form/FormErrorBanner.vue'
 import FormGrid from '../components/form/FormGrid.vue'
 import FormTabs from '../components/form/FormTabs.vue'
-import { FORM_ASSETS, FORM_ENABLED_LOCALES, FORM_LOCALE, FORM_PATCH, FORM_SESSION, FORM_VALUES, createUploadGate } from '../components/form/formContext'
+import {
+  DEPENDENT_CACHE,
+  FORM_ASSETS,
+  FORM_ENABLED_LOCALES,
+  FORM_FEEDBACK,
+  FORM_LOCALE,
+  FORM_PATCH,
+  FORM_SESSION,
+  FORM_VALUES,
+  createUploadGate,
+} from '../components/form/formContext'
+import type { AdminDependentOptionsResult } from '../api/types'
 import { RELATION_MANAGER, needsRecord } from '../components/form/registry'
 import {
   DEFAULT_TAB,
@@ -22,7 +33,9 @@ import {
   contextAllows,
   editablePayload,
   fieldErrors,
-  focusField,
+  fieldHasErrors,
+  firstErrorKey,
+  focusError,
   initialValues,
   isMLField,
   mergeMLValue,
@@ -124,7 +137,7 @@ const tabs = computed<TabItem[]>(() => {
         out.push(tab)
       }
     }
-    if (errors.value[field.name]) {
+    if (fieldHasErrors(errors.value, field.name)) {
       tab.errors += 1
     }
   }
@@ -281,6 +294,36 @@ provide(FORM_PATCH, update)
 provide(FORM_LOCALE, computed(() => schema.value?.meta.locale || currentLocale.value))
 provide(FORM_ENABLED_LOCALES, computed(() => schemaEnabledLocales(schema.value?.meta)))
 provide(FORM_ASSETS, () => assetsReady)
+// The form's single polite live region (dependent dropdown clears, repeater
+// moves) and the feedback nested controls read: errors and notices by row
+// path, the confirm dialog (Phase 17, D-07, D-08).
+const announcement = ref('')
+let announceTimer: ReturnType<typeof setTimeout> | null = null
+function announce(text: string): void {
+  // Emptied first, so the same text is announced again.
+  announcement.value = ''
+  if (announceTimer !== null) {
+    clearTimeout(announceTimer)
+  }
+  announceTimer = setTimeout(() => {
+    announceTimer = null
+    announcement.value = text
+  }, 50)
+}
+provide(FORM_FEEDBACK, {
+  errors: computed(() => errors.value),
+  notices: computed(() => notices.value),
+  clearError: (key: string) => {
+    if (errors.value[key]) {
+      const next = { ...errors.value }
+      delete next[key]
+      errors.value = next
+    }
+  },
+  announce,
+  confirm: (request) => confirm.ask(request),
+})
+provide(DEPENDENT_CACHE, new Map<string, AdminDependentOptionsResult>())
 provide(FORM_SESSION, {
   key: sessionKey,
   recordId: recordId ?? 0,
@@ -297,7 +340,8 @@ provide(FORM_SESSION, {
 /** 422: messages under fields, the first invalid field (schema order) focused. */
 async function showErrors(error: ErrorEnvelope['error'] | undefined): Promise<void> {
   errors.value = fieldErrors(error?.details)
-  const invalid = fields.value.filter((field) => errors.value[field.name])
+  // A repeater row path (content.3.answer) counts for its field.
+  const invalid = fields.value.filter((field) => fieldHasErrors(errors.value, field.name))
   const first = invalid.find((field) => tabOf(field) === activeTab.value) ?? invalid[0]
   if (!first) {
     return
@@ -306,7 +350,12 @@ async function showErrors(error: ErrorEnvelope['error'] | undefined): Promise<vo
     activeTab.value = tabOf(first)
   }
   await nextTick()
-  focusField(ID_PREFIX, first.name)
+  const key = firstErrorKey(errors.value, first.name) ?? first.name
+  if (!focusError(ID_PREFIX, key)) {
+    // A repeater row the errors opened mounts its body one tick later.
+    await nextTick()
+    focusError(ID_PREFIX, key)
+  }
 }
 
 function redirectTarget(kind: 'redirect' | 'redirectClose', id: unknown): string {
@@ -467,6 +516,9 @@ onMounted(() => {
 onBeforeUnmount(() => {
   window.removeEventListener('beforeunload', onBeforeUnload)
   window.removeEventListener(ML_LOCALE_CHANGE, onMLLocale)
+  if (announceTimer !== null) {
+    clearTimeout(announceTimer)
+  }
 })
 
 // The header's last breadcrumb is this record's title (design: Top header).
@@ -547,6 +599,8 @@ void load()
       </div>
     </footer>
 
+    <p class="sr-only" aria-live="polite" data-form-live>{{ announcement }}</p>
+
     <ConfirmDialog
       :open="confirm.request.value !== null"
       :message="confirm.request.value?.message ?? ''"