Fix menu item highlighting with aria-selected attribute

Added app_name Jinja global and aria-selected to nav menu links.
Matches by first path segment (e.g. /market/... → "market") or by
app_name for cross-domain cases (e.g. cart app → "cart" menu item).

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

browser/templates/_types/menu_items/_nav_oob.html

@@ -1,4 +1,5 @@
 {% set _app_slugs = {'cart': cart_url('/')} %}
+{% set _first_seg = request.path.strip('/').split('/')[0] %}
 <div class="flex flex-col sm:flex-row sm:items-center gap-2 border-r border-stone-200 mr-2 sm:max-w-2xl"
      id="menu-items-nav-wrapper"
      hx-swap-oob="outerHTML">
@@ -14,6 +15,7 @@
         hx-swap="outerHTML"
         hx-push-url="true"
       {% endif %}
+      aria-selected="{{ 'true' if (item.slug == _first_seg or item.slug == app_name) else 'false' }}"
       class="{{styles.nav_button}}"
     >
       {% if item.feature_image %}

browser/templates/_types/root/_nav.html

@@ -1,4 +1,5 @@
 {% set _app_slugs = {'cart': cart_url('/')} %}
+{% set _first_seg = request.path.strip('/').split('/')[0] %}
 <div class="flex flex-col sm:flex-row sm:items-center gap-2 border-r border-stone-200 mr-2 sm:max-w-2xl"
      id="menu-items-nav-wrapper">
   {% from 'macros/scrolling_menu.html' import scrolling_menu with context %}
@@ -6,6 +7,7 @@
     {% set _href = _app_slugs.get(item.slug, coop_url('/' + item.slug + '/')) %}
     <a
       href="{{ _href }}"
+      aria-selected="{{ 'true' if (item.slug == _first_seg or item.slug == app_name) else 'false' }}"
       class="{{styles.nav_button_less_pad}}"
     >
       {% if item.feature_image %}