PPTX export now writes each slide's speaker notes into the PowerPoint notes
pane (notesSlide parts + a notesMaster, wired through content-types and
relationships). Slides without notes stay note-free, so the machinery is
omitted entirely when no slide has notes. Note text is XML-escaped and
multi-line notes become separate paragraphs.
Also drop the README line pointing at the removed ci.yml workflow.
Tests: notes embedded only for noted slides, text present and escaped,
slide links to its notesSlide, and all (including notes) XML well-formed.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>