Add non-regression test for phpstan/phpstan#13857

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: phpstan-bot

tests/PHPStan/Analyser/nsrt/bug-13857.php

@@ -0,0 +1,15 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Bug13857;
+
+use function PHPStan\Testing\assertType;
+
+/**
+ * @param array<int, array{state: string}> $array
+ */
+function test(array $array, int $id): void {
+	$array[$id]['state'] = 'foo';
+	assertType("non-empty-array<int, array{state: string}>", $array);
+}