feat(16.2-01): host plugin field type elements in the admin SPA

- loadFieldTypes fetches GET /field-types after sign-in, loads each script
  once and adds the styles as global links activateStyles never disables
- PluginField creates the type's element, sets the value property and the
  contract attributes, takes summer-change as the form value and never
  writes back a value the element just emitted
- rendererForField and isRegisteredField route any field with an element
  to PluginField in forms, previews and the save payload
- rebuilt modules/boardwalk/dist

admin/src/main.ts

@@ -2,6 +2,7 @@ import { createApp } from 'vue'
 import App from './App.vue'
 import { createAdminRouter } from './app/router'
 import { onUnauthorized } from './api/client'
+import { loadFieldTypes } from './app/fieldTypes'
 import { loadStrings } from './app/i18n'
 import { applyColorScheme } from './app/theme'
 import { expireSession, me } from './state/useAuth'
@@ -13,13 +14,16 @@ async function boot(): Promise<void> {
   // Dark mode follows the system preference before anything renders (A6).
   applyColorScheme()
   // Boot order (research Pattern 7): the public strings bundle first, so the
-  // login screen is translated, then the session, then navigation.
+  // login screen is translated, then the session, then navigation and the
+  // plugin field types.
   await loadStrings().catch(() => undefined)
   // A 401 here only means "not signed in"; the router guard sends the
   // visitor to the login route with the requested path as redirect.
   const user = await me().catch(() => null)
   if (user) {
-    await Promise.all([loadNavigation().catch(() => []), loadSettings().catch(() => [])])
+    // Plugin field types load once per session: their scripts define the
+    // elements any controller's form may use, their styles stay enabled.
+    await Promise.all([loadNavigation().catch(() => []), loadSettings().catch(() => []), loadFieldTypes()])
   }
   const router = createAdminRouter()
   // A session that cannot be recovered ends here: the profile and every