Add the design system extracted from the app

design/ holds the tokens for all six themes, the type scale, spacing,
radii and sizes, the brand and usage guidelines, a guide and static
preview for each component, the logo and icons as SVG, and wireframes of
the tablet and foldable column layout.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RhmDdrN5hgWrgRcFLAMsV6

design/components/SectionLabel/README.md

@@ -0,0 +1,6 @@
+# SectionLabel
+
+The heading over each group in the reading settings sheet.
+
+- **Consumer provides:** the text.
+- `title-small` in `primary`, with `space-12` above it. Not a link and not tappable; it only names the group of chips, slider or toggle beneath.