Fix comments UX regressions and HTMX/Turnstile behavior

- standardize comment and reply UI layout
- target replies with stable OOB container IDs
- remove stale empty-state on approved HTMX comments
- initialize Turnstile widgets after HTMX swaps
- add regression tests for empty-state, OOB targets, and reply form rerender

Refs #48

templates/base.html

@@ -18,6 +18,7 @@
     <script src="{% static 'js/theme.js' %}" defer></script>
     <script src="{% static 'js/prism.js' %}" defer></script>
     <script src="{% static 'js/newsletter.js' %}" defer></script>
+    <script src="{% static 'js/comments.js' %}" defer></script>
     <script src="{% static 'js/htmx.min.js' %}" nonce="{{ request.csp_nonce|default:'' }}" defer></script>
     {% if turnstile_site_key %}<script src="https://challenges.cloudflare.com/turnstile/v0/api.js" async defer nonce="{{ request.csp_nonce|default:'' }}"></script>{% endif %}
   </head>