Per review feedback (use a real markdown parser with an AST linked to
source positions), rewrite verify-md-wrap to parse each file with
mdast-util-from-markdown (the CommonMark parser behind remark) + the GFM
extension, then flag any `paragraph` node whose source span covers more
than one line.
Why a parser over the hand-rolled line scanner:
- It is a checker, not a formatter — it reports and never rewrites, so
zero cosmetic churn (no emphasis-marker or table-delimiter
normalization, which is why Prettier was rejected for this).
- The AST owns every structural exemption (fenced code of any fence
length, tables, lists, blockquotes, HTML, headings, reference defs),
fixing both bugs the regex version had: it now catches wrapped
list-item / blockquote prose (a `paragraph` inside those nodes) and no
longer false-positives on a longer ```` fence wrapping an inner ```.
Also unwrap two pre-existing hard-wrapped blockquotes (architecture.md,
adding-a-tool.md) that the stricter AST check correctly surfaced.
