Single-page PPT authoring

Given:

• A target slide directory (typically .pptwork/<deck>/<slide-name>/)
• One outline entry (pageType, assetId, key content, source, transition)
• The deck exportMode (raster or editable)

Produce:

• design.md — frontmatter title + layout, then ## Content / ## Note / ## Design (all three sections must be non-empty)
• slide.html — single-file self-contained, with the ## Note text mirrored into a <script type="application/json" id="ppt-speaker-notes-json"> island

Out of scope: cross-page planning (use the ppt skill's story-planning phase), screenshots and visual QC (use the ppt skill's screenshot.mjs + visual-qc reference), exporting (use export.mjs), web search (use the host app's webfetch / websearch).