fix: use full date-prefixed filenames for OG images

The Nunjucks race condition in Eleventy 3.x affects page.url too —
its value changes between {% set %} and {{ }} within the same
template render during parallel builds. Instead of trying to derive
slugs from page data, name OG images with the full filename
(including date prefix) to match URL path segments exactly.

eleventy.config.js

@@ -363,11 +363,11 @@ export default function (eleventyConfig) {
   });
 
   // Derive OG slug from page.url (reliable) instead of page.fileSlug
-  // (which suffers from Nunjucks race conditions in Eleventy 3.x parallel rendering)
+  // (which suffers from Nunjucks race conditions in Eleventy 3.x parallel rendering).
+  // OG images are named with the full date prefix to match URL segments exactly.
   eleventyConfig.addFilter("ogSlug", (url) => {
     if (!url) return "";
-    const last = url.replace(/\/$/, "").split("/").pop();
-    return last.replace(/^\d{4}-\d{2}-\d{2}-/, "");
+    return url.replace(/\/$/, "").split("/").pop();
   });
 
   // Check if a generated OG image exists for this slug