Fix disabled vanity field

web/static/app.js

@@ -108,8 +108,9 @@
     submit.disabled = true;
     progress.hidden = false;
 
-    // FormData follows DOM order, so the token, expiry and vanity fields all
-    // precede the file part, which is exactly what the server requires.
+    // FormData follows markup order, not painted order, so the options and the
+    // token precede the file part exactly as the server requires. The drop
+    // zone only looks like it comes first; see the order rules in style.css.
     var data = new FormData(form);
     var started = Date.now();