Phase 4: replace container widgets with fragment fetches

Blog post page and home route fetch container-nav from events + market
concurrently via fetch_fragments(). Blog listing fetches container-cards
from events and parses per-post HTML via comment markers.
widget_paginate proxies calendar pagination to events fragment.

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

bp/post/routes.py

@@ -13,7 +13,7 @@ from quart import (
 from .services.post_data import post_data
 from .services.post_operations import toggle_post_like
 from shared.services.registry import services
-from shared.services.widget_registry import widgets
+from shared.infrastructure.fragments import fetch_fragment, fetch_fragments
 
 from shared.browser.app.redis_cacher import cache_page, clear_cache
 
@@ -69,24 +69,27 @@ def register():
           db_post_id = (g.post_data.get("post") or {}).get("id")
           post_slug = (g.post_data.get("post") or {}).get("slug", "")
 
-          # Widget-driven container nav
-          container_nav_loaded = []
-          for w in widgets.container_nav:
-              try:
-                  wctx = await w.context_fn(
-                      g.s, container_type="page", container_id=db_post_id,
-                      post_slug=post_slug,
-                  )
-                  has_data = any(v for v in wctx.values() if isinstance(v, list) and v)
-                  if has_data:
-                      container_nav_loaded.append({"widget": w, "ctx": wctx})
-              except Exception:
-                  pass
+          # Fetch container nav fragments from events + market
+          paginate_url = url_for(
+              'blog.post.widget_paginate',
+              slug=post_slug, widget_domain='calendar',
+          )
+          nav_params = {
+              "container_type": "page",
+              "container_id": str(db_post_id),
+              "post_slug": post_slug,
+              "paginate_url": paginate_url,
+          }
+          events_nav_html, market_nav_html = await fetch_fragments([
+              ("events", "container-nav", nav_params),
+              ("market", "container-nav", nav_params),
+          ])
+          container_nav_html = events_nav_html + market_nav_html
 
           ctx = {
               **p_data,
               "base_title": f"{config()['title']} {p_data['post']['title']}",
-              "container_nav_widgets": container_nav_loaded,
+              "container_nav_html": container_nav_html,
           }
 
           # Page cart badge via service
@@ -154,20 +157,22 @@ def register():
 
   @bp.get("/w/<widget_domain>/")
   async def widget_paginate(slug: str, widget_domain: str):
-      """Generic paginated widget endpoint for infinite scroll."""
+      """Proxies paginated widget requests to the appropriate fragment provider."""
       page = int(request.args.get("page", 1))
       post_id = g.post_data["post"]["id"]
 
-      for w in widgets.container_nav:
-          if w.domain == widget_domain:
-              ctx = await w.context_fn(
-                  g.s, container_type="page", container_id=post_id,
-                  post_slug=slug, page=page,
-              )
-              html = await render_template(
-                  w.template, ctx=ctx, post=g.post_data["post"],
-              )
-              return await make_response(html)
+      if widget_domain == "calendar":
+          html = await fetch_fragment("events", "container-nav", params={
+              "container_type": "page",
+              "container_id": str(post_id),
+              "post_slug": slug,
+              "page": str(page),
+              "paginate_url": url_for(
+                  'blog.post.widget_paginate',
+                  slug=slug, widget_domain='calendar',
+              ),
+          })
+          return await make_response(html or "")
       abort(404)
 
   return bp