File ▸ Open's Outline filter accepts `.md`, but a `.md` was read with the
plain outline format (unindented line = slide, indent = bullet), so a
Markdown outline written the usual way kept `#` in its titles and made
every top-level list item a slide of its own.
`deckcraft_format::markdown_to_slides` reads ATX headings (`#`–`######`,
closing `#`s dropped) as slide titles, list items (`-`, `*`, `+`, `1.`,
`1)`) as bullets nested by their indentation, and other lines under a
heading as body paragraphs. A `.md` without headings is still read as a
plain outline, so existing indented `.md` outlines open as before; `.txt`
is unchanged. Opening a `.md` and dropping one on the window
(`slide.fromOutline {markdown: true}`) use it. Both readers now share the
slide builder.
Tests: the outline from the issue (2 slides, nested bullets), numbered and
`*`/`+` lists with text under a heading, `slide.fromOutline` with
`markdown`, plain `.txt`/`.md` outlines unchanged, and heading / list-item
edge cases (not-a-heading forms, closing hashes, Unicode, long digit runs).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
