Add ThemeKit Configurator web app

[rozd]

Summary

• Add a Svelte SPA (.github/pages/) that lets users visually build theme.json instead of editing JSON by hand
• Schema-driven UI — categories, token fields, and config options are all derived from theme.schema.json at runtime
• Dark mode support with system preference detection and manual toggle
• Download button for the generated JSON output
• Warns when token names conflict with SwiftUI built-in ShapeStyle properties (e.g. .primary, .background) and prompts users to set a custom style override
• GitHub Pages deployment workflow (.github/workflows/deploy-pages.yml)

Test plan

• npm run build in .github/pages/ succeeds
• Add a token named primary → red highlight + warning icon with tooltip
• Open popover for conflicting token → warning hint visible above style input
• Type primaryColor in style field → warning disappears, override highlight appears
• Clear style field → warning reappears
• Add token named surface (not a built-in) → no warning
• Toggle dark mode — UI adapts correctly
• Download button produces valid theme.json

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.30%. Comparing base (0bbc244) to head (add667f).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main       #6   +/-   ##
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  Coverage   99.30%   99.30%           
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  Files          28       28           
  Lines        1154     1154           
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  Hits         1146     1146           
  Misses          8        8           

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