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>
Rename all sexp directories, files, identifiers, and references to sx.
artdag/ excluded (separate media processing DSL).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>