yuehancn/dsh-tool-notion

Convert Notion blocks and Markdown in both directions, with no API client and no external dependency. A Notion paragraph is an array of rich-text runs while Markdown says one string, so the two directions are a split and a merge rather than a pair of inverses — rich-text runs are cut at every annotation boundary one way and re-merged the other, with fences widened when the content already contains backticks. Reports every lossy step instead of swallowing it.