fix: exclude .well-known/llms.txt from starlight link validator

sameSitePolicy validate rewrites aptos.dev URLs to paths; /.well-known/llms.txt
strips to .well-known/... which the plugin treats as a relative link. The URL is
served by Vercel redirect, not a Starlight page, so skip validation.

Author: cursoragent

astro.config.mjs

@@ -144,6 +144,13 @@ export default defineConfig({
               return true;
             }
 
+            // Same-site absolute URL becomes `/.well-known/llms.txt`; after stripping `/` the path
+            // starts with `.` and is misclassified as a relative link. Production serves this via
+            // Vercel redirect to /llms.txt, not as a doc route.
+            if (link.includes("/.well-known/llms.txt")) {
+              return true;
+            }
+
             // Exclude specific problematic links from external move-reference content
             const excludeLinks = [
               "https://aptos.dev/move/book/SUMMARY",