DL-637

jj-vine treats a whole-line stack marker as real only when pulldown-cmark starts an HTML block at it, so marker examples in code or HTML blocks stay user text; the writer keeps a layout only when that reader finds the new block in it again, else it puts the block at the top, else it returns the PR’s current description unchanged and warns.

Status: Active (RIG-5587 design, 2026-10-20)