docs(marketing): use folder in annotate description, keep dir in param placeholder

For provenance purposes, this commit was AI assisted.

Author: backnotprop

apps/marketing/src/pages/index.astro

@@ -316,7 +316,7 @@ import AnnoReplace from '../components/landing/AnnoReplace.astro';
             </div>
             <div class="cap-item">
               <code class="cap-cmd">/plannotator-annotate &lt;file|dir|url&gt;</code>
-              <span class="cap-desc">Annotate any markdown, html, dir, or URL and send feedback</span>
+              <span class="cap-desc">Annotate any markdown, html, folder, or URL and send feedback</span>
             </div>
             <div class="cap-item">
               <code class="cap-cmd">/plannotator-last</code>