fix: use 11tydata.js for conditional about page permalink

Using a JavaScript data file to return boolean false for permalink
when about.md exists, instead of trying to compute it in Nunjucks
which returns string "false" and causes errors.

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

about.11tydata.js

@@ -0,0 +1,21 @@
+// Template data file for about.njk
+// Dynamically sets permalink based on whether about.md exists in content/pages/
+import { existsSync } from "fs";
+import { resolve, dirname } from "path";
+import { fileURLToPath } from "url";
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+
+export default function() {
+  // Check for about.md in content/pages/ directory
+  const aboutPath = resolve(__dirname, "content/pages/about.md");
+  const aboutExists = existsSync(aboutPath);
+
+  return {
+    // If about.md exists, disable this template's permalink
+    // If not, use /about/ as the permalink
+    permalink: aboutExists ? false : "/about/",
+    // Also exclude from collections if about.md exists
+    eleventyExcludeFromCollections: aboutExists
+  };
+}

about.njk

@@ -1,8 +1,6 @@
 ---
 layout: layouts/base.njk
 title: About
-eleventyComputed:
-  permalink: "{% set aboutPageExists = false %}{% for page in collections.pages %}{% if page.fileSlug == 'about' %}{% set aboutPageExists = true %}{% endif %}{% endfor %}{% if aboutPageExists %}false{% else %}/about/{% endif %}"
 ---
 <article class="h-card">
   <header class="mb-6 sm:mb-8 flex flex-col sm:flex-row gap-6 sm:gap-8 items-start">