feat(ui): render application templates as Vue views mounted before wiring

Templates listed in build/applicationViews.js expand to mount hosts, and
mountApplicationViews() renders them before translation and wiring. Markup
tests read the page through a server-side render helper, the i18n scanner
reads view templates, and Vue preserves whitespace so views keep the exact
DOM. No template is converted yet.

src/app/application.js

@@ -1,3 +1,4 @@
+import { mountApplicationViews } from '../ui/views/index.js';
 const START_ORDER = ['scene', 'controls', 'data', 'tools'];
 // Controls cancel restoration while the data manager and viewer still exist.
 const STOP_ORDER = ['tools', 'controls', 'data', 'scene'];
@@ -15,6 +16,8 @@ export function createApplication({
   createData,
   createTools,
 }) {
+  // A host's page needs its views before any phase reads the markup.
+  mountApplicationViews();
   const factories = {
     scene: createScene,
     controls: createControls,