v4.27.1 — a clean report was marked failed over a tool nobody asks you to install

Fixed — a clean report was marked failed over a tool nobody asks you to install

Found by installing 4.27.0 from PyPI into an empty environment and running the
example, which is the first thing anyone reading the README will do.

• An optional toolchain's failure is no longer the document's verdict.
  VISUAL_RENDER_CHECK shells out to LibreOffice and Poppler. 4.26.0 already
  excluded their absence from the delivery verdict; a broken installation
  was not excluded, so a stale soffice shim on PATH made the check run, fail,
  and drag a report that passed every gate to Overall status: failed —
  in published/qa/final_qa_summary.md, the page AGENTS.md tells a reader to
  open first. The same failure text also reached the render-issue list quoted
  from a console in another encoding, so the stated reason was a row of
  replacement characters. The check is still run and still reported verbatim as
  visual_render_status; it no longer feeds render_status. Anyone who does
  want it enforced still has strict_visual_render_check, which hard-blocks
  inside the check itself.

The branch that was fixed and the branch beside it were written at the same
time; only the reported one was changed. That is the third time in this
repository that a defect's neighbour survived its fix.