Re-staged from the contributor's rebased head (0cee92c9) which independently converged on
the same 5-test-file class-tolerance fixups I'd made — shipping the contributor's exact
version, not my private variant. Tags md/markdown/mdx fenced blocks with md-source-block
class in both renderers; CSS wraps them while code/diff/csv keep horizontal-scroll. 90
renderer-family tests pass.
Co-authored-by: nesquena-hermes <agent@nesquena-hermes>
Co-authored-by: TomBanksAU <TomBanksAU@users.noreply.github.com>
nesquena-hermes