feat: add e2e test harness (#1237)

Co-authored-by: Christian Pillsbury <cpillsbury@mux.com>

apps/e2e/scripts/sync-ejected-skins.ts

@@ -0,0 +1,37 @@
+/**
+ * Syncs the generated ejected skin source from the docs site build
+ * into the e2e test app so the ejected React test uses real output.
+ *
+ * Run after `pnpm -F site ejected-skins` and before e2e tests.
+ */
+
+import { mkdirSync, readFileSync, writeFileSync } from 'node:fs';
+import { resolve } from 'node:path';
+
+const EJECTED_SKINS_JSON = resolve(import.meta.dirname, '../../../site/src/content/ejected-skins.json');
+const OUT_DIR = resolve(import.meta.dirname, '../apps/vite/src/_generated');
+
+interface EjectedSkinEntry {
+  id: string;
+  platform: string;
+  tsx?: string;
+  css?: string;
+}
+
+const skins: EjectedSkinEntry[] = JSON.parse(readFileSync(EJECTED_SKINS_JSON, 'utf-8'));
+
+const reactVideo = skins.find((s) => s.id === 'default-video-react');
+
+if (!reactVideo?.tsx) {
+  throw new Error('Ejected skin "default-video-react" not found. Run `pnpm -F site ejected-skins` first.');
+}
+
+mkdirSync(OUT_DIR, { recursive: true });
+
+writeFileSync(resolve(OUT_DIR, 'ejected-react-video-skin.tsx'), reactVideo.tsx);
+
+if (reactVideo.css) {
+  writeFileSync(resolve(OUT_DIR, 'player.css'), reactVideo.css);
+}
+
+console.log('Synced ejected React video skin to apps/e2e/apps/vite/src/_generated/');