fix: remediate phpstan errors

inc/Modules/Search/Search.php

@@ -38,7 +38,7 @@ final class Search implements Registrable {
 	 *
 	 * @var bool|null
 	 */
-	private ?bool $is_search_enabled;
+	private ?bool $is_search_enabled = null;
 
 	/**
 	 * {@inheritDoc}

phpstan.neon.dist

@@ -21,6 +21,8 @@ parameters:
 		max: 80500
 	bootstrapFiles:
 		- onesearch.php
+	stubFiles:
+		- phpstan/stubs/wordpress-extended.php
 	paths:
 		- onesearch.php
 		- uninstall.php

phpstan/stubs/wordpress-extended.php

@@ -0,0 +1,29 @@
+<?php // phpcs:disable -- This is a stub file
+/**
+ * Extends WP_Query and WP_Post with OneSearch dynamic properties for PHPStan analysis.
+ */
+
+namespace {
+	/**
+	 * Extended WP_Query with OneSearch dynamic properties.
+	 *
+	 * @property bool $is_algolia_search Whether this is an Algolia-powered search query.
+	 */
+	class WP_Query {
+	}
+
+	/**
+	 * Extended WP_Post with OneSearch dynamic properties.
+	 *
+	 * @property array<string, string> $onesearch_algolia_highlights Highlighted search snippets from Algolia.
+	 * @property string                 $onesearch_site_url URL of the site this post belongs to.
+	 * @property string                 $onesearch_site_name Name of the site this post belongs to.
+	 * @property string                 $onesearch_remote_post_author_display_name Remote author display name.
+	 * @property string                 $onesearch_remote_post_author_link Remote author posts URL.
+	 * @property string                 $onesearch_remote_post_author_gravatar Remote author avatar URL.
+	 * @property int                    $onesearch_original_id Original post ID on remote site.
+	 * @property array<string, mixed>   $onesearch_remote_taxonomies Taxonomies from remote site.
+	 */
+	class WP_Post {
+	}
+}