Add isolated Pages demo mode with sample vault data

scripts/pages-spa-redirects.cjs

@@ -0,0 +1,7 @@
+const fs = require('node:fs');
+const path = require('node:path');
+
+const distDir = path.resolve(__dirname, '..', 'dist');
+
+fs.mkdirSync(distDir, { recursive: true });
+fs.writeFileSync(path.join(distDir, '_redirects'), '/* /index.html 200\n');