Wire sx_content through full read/write pipeline

Model: add sx_content column to Post. Writer: accept sx_content in
create_post, create_page, update_post. Routes: read sx_content from form
data in new post, new page, and edit routes. Read pipeline: ghost_db
includes sx_content in public dict, detail/home views prefer sx_content
over html when available, PostDTO includes sx_content.

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

blog/bp/blog/ghost_db.py

@@ -63,6 +63,7 @@ def _post_to_public(p: Post) -> Dict[str, Any]:
         "slug": p.slug,
         "title": p.title,
         "html": p.html,
+        "sx_content": p.sx_content,
         "is_page": p.is_page,
         "excerpt": p.custom_excerpt or p.excerpt,
         "custom_excerpt": p.custom_excerpt,

blog/bp/blog/routes.py

@@ -265,6 +265,7 @@ def register(url_prefix, title):
         return await make_response(html, 400)
 
       # Create directly in db_blog
+      sx_content_raw = form.get("sx_content", "").strip() or None
       post = await writer_create(
           g.s,
           title=title,
@@ -274,6 +275,7 @@ def register(url_prefix, title):
           feature_image=feature_image or None,
           custom_excerpt=custom_excerpt or None,
           feature_image_caption=feature_image_caption or None,
+          sx_content=sx_content_raw,
       )
       await g.s.flush()
 
@@ -337,6 +339,7 @@ def register(url_prefix, title):
         return await make_response(html, 400)
 
       # Create directly in db_blog
+      sx_content_raw = form.get("sx_content", "").strip() or None
       page = await writer_create_page(
           g.s,
           title=title,
@@ -346,6 +349,7 @@ def register(url_prefix, title):
           feature_image=feature_image or None,
           custom_excerpt=custom_excerpt or None,
           feature_image_caption=feature_image_caption or None,
+          sx_content=sx_content_raw,
       )
       await g.s.flush()
 

blog/bp/post/admin/routes.py

@@ -562,6 +562,7 @@ def register():
     elif status and status != current_status:
       effective_status = status
 
+    sx_content_raw = form.get("sx_content", "").strip() or None
     try:
       post = await writer_update(
           g.s,
@@ -573,6 +574,7 @@ def register():
           custom_excerpt=custom_excerpt or None,
           feature_image_caption=feature_image_caption or None,
           status=effective_status,
+          sx_content=sx_content_raw,
       )
     except OptimisticLockError:
       return redirect(