feat(wpmc S2): Taxonomy::register() attaches init hook

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

includes/class-taxonomy.php

@@ -0,0 +1,19 @@
+<?php
+declare(strict_types=1);
+
+namespace WPMultiCity;
+
+final class Taxonomy
+{
+    public const SLUG = 'town';
+
+    public static function register(): void
+    {
+        add_action('init', [self::class, 'do_register']);
+    }
+
+    public static function do_register(): void
+    {
+        // Implementation filled in Task 5.
+    }
+}

tests/TaxonomyTest.php

@@ -0,0 +1,43 @@
+<?php
+declare(strict_types=1);
+
+namespace WPMultiCity\Tests;
+
+use Brain\Monkey\Actions;
+use WPMultiCity\Taxonomy;
+
+final class TaxonomyTest extends TestCase
+{
+    public function test_register_attaches_init_action(): void
+    {
+        Taxonomy::register();
+
+        self::assertNotFalse(
+            has_action('init', [Taxonomy::class, 'do_register']),
+            'Taxonomy::register() must attach init action with do_register handler'
+        );
+    }
+
+    public function test_do_register_calls_register_taxonomy_town_with_required_args(): void
+    {
+        $captured = null;
+        \Brain\Monkey\Functions\expect('register_taxonomy')
+            ->once()
+            ->with('town', ['shortcode-town'], \Mockery::on(function ($args) use (&$captured) {
+                $captured = $args;
+                return true;
+            }));
+
+        Taxonomy::do_register();
+
+        self::assertFalse($captured['hierarchical'], 'town must be flat');
+        self::assertFalse($captured['public'], 'town must not be public');
+        self::assertTrue($captured['show_ui'], 'town must show in admin UI');
+        self::assertTrue($captured['show_in_rest'], 'town must be REST-exposed');
+        self::assertFalse($captured['publicly_queryable']);
+        self::assertFalse($captured['query_var']);
+        self::assertFalse($captured['rewrite']);
+        self::assertFalse($captured['meta_box_cb']);
+        self::assertSame('Города', $captured['labels']['name']);
+    }
+}