Add shared/sx/html_to_sx.py (HTMLParser-based HTML→sx converter) and
update lexical_to_sx.py so HTML cards, markdown cards, and captions all
produce native sx expressions instead of opaque HTML strings.
- ~kg-html now wraps native sx children (editor can identify the block)
- New ~kg-md component for markdown card blocks
- Captions are sx expressions, not escaped HTML strings
- kg_cards.sx: replace (raw! caption) with direct caption rendering
- sx-editor.js: htmlToSx() via DOMParser, serializeInline for captions,
_childrenSx for ~kg-html/~kg-md, new kg-md edit UI
- Migration script (blog/scripts/migrate_sx_html.py) to re-convert
stored sx_content from lexical source
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
giles
8ceb9aee62