fix: Multi-layer protection against Twig rendering recursion

- Added render depth tracking in Plugin::render() with max depth of 5
- Strip shortcodes from content when in shortcode context
- Prevents any later do_shortcode() calls from triggering recursion

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

includes/Frontend/TemplateLoader.php

@@ -270,10 +270,19 @@ class TemplateLoader {
             $excerpt = get_the_excerpt( $post );
         }
 
+        // When skipping content filter, also strip shortcodes to prevent them from
+        // being processed by anything else that might call do_shortcode on the output.
+        if ( $skip_content_filter ) {
+            $content = strip_shortcodes( $post->post_content );
+            $content = wp_kses_post( $content );
+        } else {
+            $content = apply_filters( 'the_content', $post->post_content );
+        }
+
         $data = array(
             'id'        => $post->ID,
             'title'     => get_the_title( $post ),
-            'content'   => $skip_content_filter ? wp_kses_post( $post->post_content ) : apply_filters( 'the_content', $post->post_content ),
+            'content'   => $content,
             'excerpt'   => $excerpt,
             'permalink' => get_permalink( $post ),
             'thumbnail' => get_the_post_thumbnail_url( $post->ID, 'large' ),