Fix letrec structure: wait-for-el as proper binding, not begin-wrapped

The previous insert wrapped reload-frame and wait-for-el in a begin
block instead of making them separate letrec bindings. This made
reload-frame invisible to later bindings. Fixed by inserting
wait-for-el at index 3 in the letrec bindings list.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

sx/sx/applications/htmx/runner.sx

@@ -24,7 +24,6 @@
                     "true"))
                 true
                 (do (hs-wait 200) (wait-boot))))))
-        (begin
         (reload-frame
           (fn
             ()
@@ -46,7 +45,7 @@
                 (if
                   (<= max-tries 0)
                   nil
-                    (do (hs-wait 200) (wait-for-el sel (- max-tries 1)))))))))
+                  (do (hs-wait 200) (wait-for-el sel (- max-tries 1))))))))
         (run-action
           (fn
             (action)