Replace _post_edit_content_sx raw HTML builder with sx_call() pattern
matching render_editor_panel. Add ~blog-editor-edit-form,
~blog-editor-publish-js, ~blog-editor-sx-initial components to
editor.sx. Fixes (~sx-editor-styles) rendering as literal text on
the edit page.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>