fix: remove wp_kses_post() HTML escaping from REST API JSON output

The security audit added wp_kses_post()/esc_html() to article fields
before returning them via the REST API. This caused double-encoding
(e.g., & → &) because REST responses are JSON, not HTML —
WordPress's rest_ensure_response() already handles JSON encoding.
The frontend is responsible for output escaping at render time.

Removes the 4 escaping lines from get_articles() to fix broken
summaries and truncated content on the live site.

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

includes/class-peptide-news-rest-api.php

@@ -185,11 +185,6 @@ class Peptide_News_Rest_API {
                 }
             }
 
-            // Escape string fields for REST API output
-            $article->title     = wp_kses_post( $article->title );
-            $article->excerpt   = wp_kses_post( $article->excerpt );
-            $article->ai_summary = wp_kses_post( $article->ai_summary );
-            $article->author    = esc_html( $article->author );
         }
 
         $data = array(