Markdown sources

One file per item, with YAML front matter. 247 files: 246 carry the article text, the other 1 are audio or video and hold metadata only, since the archive links to those rather than transcribing them. The short posts are not here — they have no Markdown source and come from social-posts.json. For bulk use prefer index.json (metadata for every record, full text where available) or all.md.