feat(wpmc S3): Helpers scaffold + reset_cache wiring

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

includes/class-helpers.php

@@ -0,0 +1,18 @@
+<?php
+declare(strict_types=1);
+
+namespace WPMultiCity;
+
+final class Helpers
+{
+    private static ?string $current_town_memo = null;
+    private static bool $current_town_resolved = false;
+    private static array $term_cache = [];
+
+    public static function reset_cache(): void
+    {
+        self::$current_town_memo = null;
+        self::$current_town_resolved = false;
+        self::$term_cache = [];
+    }
+}

tests/TestCase.php

@@ -5,6 +5,7 @@ namespace WPMultiCity\Tests;
 
 use Brain\Monkey;
 use PHPUnit\Framework\TestCase as BaseTestCase;
+use WPMultiCity\Helpers;
 
 abstract class TestCase extends BaseTestCase
 {
@@ -13,6 +14,7 @@ abstract class TestCase extends BaseTestCase
         parent::setUp();
         Monkey\setUp();
         Monkey\Functions\stubTranslationFunctions();
+        Helpers::reset_cache();
     }
 
     protected function tearDown(): void