feat(widgets): rebuild admin widgets page to match reference theme

- Replace transfer modal/admin-post flow with reference-style AJAX
  export/import/template dialogs (admin-transfer.js, TransferController)
- Customizer "移出模块" action, reference lazy form loading with t-notice
- Common fields use reference labels, dependencies, compact/inline rows,
  top/bottom-only extra spacing; form header with description/reminder
- Remove placement hint, template preview and legacy transfer code
- Fix widget audit (current_datetime stub, honor catalog common flags)
  and regenerate stale golden fixtures for posts_toc, quote, posts

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/WidgetSystem/Runtime.php

@@ -24,7 +24,6 @@ final class Runtime {
 			(new RestController())->register_routes();
 		});
 		add_action('wp_enqueue_scripts', [AssetManager::class, 'enqueue_active'], 20);
-		add_action('in_widget_form', [self::class, 'render_placement_hint'], 20, 1);
 
 		AdminFormController::register_hooks();
 		TransferController::register_hooks();
@@ -48,21 +47,4 @@ final class Runtime {
 			register_widget(new SchemaWidget($definition));
 		}
 	}
-
-	public static function render_placement_hint(\WP_Widget $widget): void {
-		if (!$widget instanceof SchemaWidget) {
-			return;
-		}
-		$definition = $widget->definition();
-		$messages = [
-			'wide'    => __('宽版模块：建议放入全宽或主内容区域；放入侧栏时会显示尺寸警告。', 'aksrt'),
-			'sidebar' => __('侧栏模块：建议放入侧栏区域；放入全宽区域时会显示尺寸警告。', 'aksrt'),
-			'any'     => __('自适应模块：可放入主内容、全宽或侧栏区域。', 'aksrt'),
-		];
-		printf(
-			'<p class="aksrt-widget-placement-hint" data-widget-size="%1$s"><span class="dashicons dashicons-info-outline" aria-hidden="true"></span>%2$s</p>',
-			esc_attr($definition->size()),
-			esc_html($messages[$definition->size()] ?? $messages['any'])
-		);
-	}
 }