Fix lint: make scripts/demo/router.php PSR-12 compliant; tidy demo scripts

scripts/demo/router.php

@@ -1,6 +1,16 @@
 <?php
-$p = parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH);
-$f = __DIR__ . '/tinker' . $p;
-if ($p !== '/' && is_file($f) && !str_ends_with($f, '.php')) { return false; }
+
+/**
+ * Router script for PHP's built-in web server, used only for the local screenshot demo.
+ * Serves real static files directly and sends everything else to the application's index.php.
+ */
+
+$path = parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH);
+$file = __DIR__ . '/tinker' . $path;
+
+if ($path !== '/' && is_file($file) && !str_ends_with($file, '.php')) {
+    return false;
+}
+
 chdir(__DIR__ . '/tinker');
 require __DIR__ . '/tinker/index.php';