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.

build/application-html.js

@@ -1,4 +1,5 @@
 import { readFileSync } from 'node:fs';
+import { APPLICATION_VIEW_NAMES } from './applicationViews.js';
 
 export const APPLICATION_TEMPLATES = Object.freeze([
   'scene-chrome',
@@ -12,6 +13,16 @@ export const APPLICATION_TEMPLATES = Object.freeze([
   'hud-loading',
 ]);
 const allowed = new Set(APPLICATION_TEMPLATES);
+const views = new Set(APPLICATION_VIEW_NAMES);
+
+/**
+ * The element a Vue view renders into. `display: contents` keeps the view's
+ * own elements laid out as children of the page.
+ * @param {string} name Application template name.
+ */
+export function applicationViewHost(name) {
+  return `<div class="gev-view" data-gev-view="${name}"></div>\n`;
+}
 
 /** Expand only known component templates; markers cannot name filesystem paths. */
 export function expandApplicationHtml(html) {
@@ -20,6 +31,7 @@ export function expandApplicationHtml(html) {
     (_, name) => {
       if (!allowed.has(name))
         throw new Error(`Unknown application template: ${name}`);
+      if (views.has(name)) return applicationViewHost(name);
       return readFileSync(
         new URL(`../src/ui/templates/${name}.html`, import.meta.url),
         'utf8',