fix: read ae_hide_menu URL param and apply to sys_menu.hide in layout

The URL builder generates ae_hide_menu=true but nothing consumed it.
Now layout.svelte reads the param on mount and sets $ae_loc.sys_menu.hide,
which flows through bind:hide into E_app_sys_bar's class:hidden.

Applies even for trusted_access users who bypass the iframe guard.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/routes/+layout.svelte

@@ -254,6 +254,13 @@
         if (iframe === 'true') $ae_loc.iframe = true;
         else if (iframe === 'false') $ae_loc.iframe = false;
 
+        // ae_hide_menu=true — suppress the AE system bar when embedding in Novi or
+        // other host pages with their own navigation. Applies even for trusted_access
+        // users who would otherwise always see the menu in iframe mode.
+        if (data.url.searchParams.get('ae_hide_menu') === 'true') {
+            $ae_loc.sys_menu.hide = true;
+        }
+
         // Theme URL params — ?theme=AE_Firefly_SteelBlue&theme_mode=dark
         // Applied once on load, then silently removed from the URL (no history entry).
         const url_theme = data.url.searchParams.get('theme');