fix: address Phase 1 code review findings

- Serve cache via template_redirect so feeds/404/REST are excluded and
  query conditionals work
- Bypass cache on query strings; key files by md5(host+path) to avoid
  collisions and support multisite
- Write wp-content/wp-recache-cache.php drop-in server and set WP_CACHE
  in wp-config.php so advanced-cache.php actually runs
- Only remove advanced-cache.php on deactivation when it is ours
- Respect DONOTCACHEPAGE, non-200 responses; bots read but never warm
  cache
- Fix comment purge (comment_post_ID) and heartbeat purge ($data arg)
- Fix exclude URLs textarea parsing; purge all when exclusions change
- Enqueue admin purge script on every admin-bar page, not just settings
- Sync tests, add TESTING.md manual test guide

includes/Admin/Admin.php

@@ -19,11 +19,9 @@ class WP_Recache_Admin {
         add_action('wp_ajax_wp_recache_purge_all', [$this, 'ajax_purge_all']);
         add_action('wp_ajax_wp_recache_purge_url', [$this, 'ajax_purge_url']);
         add_action('admin_notices', [$this, 'admin_notices']);
-
-        wp_localize_script('jquery', 'wpRecache', [
-            'ajaxUrl' => admin_url('admin-ajax.php'),
-            'nonce' => wp_create_nonce('wp_recache_nonce'),
-        ]);
+        add_action('admin_enqueue_scripts', 'wp_recache_enqueue_admin_bar_script');
+        // New exclusions must not leave stale files that the drop-in would still serve.
+        add_action('update_option_wp_recache_exclude_urls', 'wp_recache_delete_all_cache');
     }
 
     /**
@@ -93,11 +91,13 @@ class WP_Recache_Admin {
      * @return array Sanitized URLs.
      */
     public function sanitize_exclude_urls($input) {
-        if (!is_array($input)) {
-            return [];
+        if (is_array($input)) {
+            $input = implode("\n", $input);
         }
 
-        return array_map('sanitize_text_field', $input);
+        $lines = array_filter(array_map('trim', explode("\n", (string) $input)));
+
+        return array_map('sanitize_text_field', $lines);
     }
 
     /**
@@ -110,6 +110,10 @@ class WP_Recache_Admin {
 
         $active_tab = isset($_GET['tab']) ? sanitize_text_field($_GET['tab']) : 'cache';
 
+        if (!in_array($active_tab, ['cache', 'optimize', 'advanced'], true)) {
+            $active_tab = 'cache';
+        }
+
         include WP_RECACHE_INC_PATH . 'Admin/views/settings.php';
     }