<!-- proptest::idempotent + html_preserving shrunk 2026-05-14 -->
<!-- PENDING: deferred to session 13b. -->
<!-- root cause: default ListMarkerStyle::Dash normalizes the `*`
     markers below to `-`. The source has two distinct lists
     separated by a blank line; after normalization both lists use
     `-`, and on re-parse pulldown-cmark sees a single 3-item loose
     list. HTML semantics change (two <ul> become one) and the
     second format pass therefore emits all three items with the
     loose-list blank-line discipline.

     Fix sketch: when emitting a list whose normalized marker
     matches the prior block's marker (also a list), choose a
     fallback marker (e.g. `+` if the chosen style is `-`) for one
     of the two lists, or skip normalization for the second. -->
- a

* a
* a
