feat(12.2-04): edit related records in modals and defer relation work on new records

- RelationManager renders create/link/delete/unlink in declared order with
  one primary, opens the child modal (update or view form) or the pivot
  modal on row click, and deletes selected children behind a busy confirm
- RelationChildModal creates and edits children with its own session key
  (X-Child-Session-Key) so uploads and dates work inside it
- RelationPivotModal edits link details; the picker links one record with
  its pivot values when the relation has a pivot form
- deferrable managers render on the create screen with owner id 0, the
  form's X-Session-Key and the pending note, and mark the form dirty
- the registry resolves RelationManager lazily (child forms close an
  import cycle); DataTable gains openable rows and a trailing cell
- relation lang keys in en and pl; rebuilt boardwalk dist

admin/src/views/FormView.vue

@@ -14,7 +14,7 @@ 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_LOCALE, FORM_PATCH, FORM_SESSION, FORM_VALUES } from '../components/form/formContext'
-import { needsRecord } from '../components/form/registry'
+import { RELATION_MANAGER, needsRecord } from '../components/form/registry'
 import {
   DEFAULT_TAB,
   contextAllows,
@@ -82,9 +82,13 @@ const revision = ref(0)
 
 // A relation manager needs a saved record: on create it is dropped with its
 // tab even when the YAML forgets `context: update` (D-05, design screen 5).
+// A deferrable one (Phase 12.2, D-03) stays: it works on owner id 0 with the
+// form's session key and the save commits its changes.
 const fields = computed(() =>
   (schema.value?.fields ?? []).filter(
-    (field) => contextAllows(field, mode) && (mode === 'update' || !needsRecord(field.type)),
+    (field) =>
+      contextAllows(field, mode) &&
+      (mode === 'update' || !needsRecord(field.type) || (field.type === RELATION_MANAGER && !!field.deferrable)),
   ),
 )
 const fieldNames = computed(() => fields.value.map((field) => field.name))