Authoring open-slide pages

This skill is the technical reference for everything that happens inside slides/<id>/index.tsx. It does not own a workflow:

• create-slide owns "draft a new deck", it asks the user scoping questions, then delegates the how to this skill.
• apply-comments owns "process inspector markers", it finds markers and applies edits, but the edits themselves follow the rules here.
• current-slide resolves deictic references ("this page", "the slide I'm on") to a concrete slideId + pageIndex. Consult it first when the user references the current slide without naming it, then come back here for how to edit it.
• Any ad-hoc slide edit (manual tweak, one-off fix) should also consult this skill before touching the file.

When any of those paths reach the point of writing React code for a page, this is the source of truth. Do not duplicate the knowledge below into other skills, link here instead.

Primitive references

Each framework primitive has a full reference file under references/ in this skill, contract, worked examples, and its own anti-patterns. This file keeps only the always-on rules and a short summary per primitive. Read the relevant reference file before using a primitive on a page:

Primitive	Read before	File
design const + var(--osd-X) tokens	writing any new slide (default baseline)	references/design-system.md
Assets + <ImagePlaceholder>	importing images/videos or leaving a placeholder	references/assets.md
Webfonts	loading any non-system font	references/webfonts.md
useSlidePageNumber()	rendering a page-number footer	references/page-numbers.md
<Steps> / <Step>	staging a page's reveal	references/steps.md
SlideTransition	declaring any enter/exit animation	references/transitions.md
MorphElement + morph	morphing a shared element across pages	references/morph.md

Hard rules