feat(wpmc S2): Plugin::boot() wires Taxonomy + PostType + FieldGroup

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

includes/class-plugin.php

@@ -41,7 +41,9 @@ final class Plugin
             return;
         }
 
-        // Stage 2-5 hooks register here. Stage 1 (skeleton) intentionally empty.
+        Taxonomy::register();
+        PostType::register();
+        FieldGroup::register();
     }
 
     private function dependencies_satisfied(): bool

tests/PluginBootTest.php

@@ -0,0 +1,32 @@
+<?php
+declare(strict_types=1);
+
+namespace WPMultiCity\Tests;
+
+use WPMultiCity\Plugin;
+
+final class PluginBootTest extends TestCase
+{
+    public function test_boot_attaches_init_and_acf_init_hooks_when_acf_present(): void
+    {
+        // Simulate ACF being active so boot() proceeds past the dependency guard.
+        if (!class_exists('ACF', false)) {
+            eval('class ACF {}');
+        }
+
+        Plugin::instance()->boot();
+
+        self::assertNotFalse(
+            has_action('init', ['WPMultiCity\\Taxonomy', 'do_register']),
+            'boot() must register Taxonomy on init'
+        );
+        self::assertNotFalse(
+            has_action('init', ['WPMultiCity\\PostType', 'do_register']),
+            'boot() must register PostType on init'
+        );
+        self::assertNotFalse(
+            has_action('acf/init', ['WPMultiCity\\FieldGroup', 'do_register']),
+            'boot() must register FieldGroup on acf/init'
+        );
+    }
+}