[codex] Bundle design system assets in projects

[jamesrochabrun]

Summary

• Bundle custom design-system reusable assets into new projects alongside resources/design-system/DESIGN.md.
• Copy extracted Figma assets to resources/design-system/resources/figma-extracted/ and manually imported assets to resources/design-system/resources/imported-assets/.
• Update README/runtime agent guidance so downstream prototype work can discover and reuse those bundled assets.

Validation

• swift test --package-path Packages/EaselChat --filter EaselChatTests

Notes

• SwiftPM test execution required a local-only ignored checkout fix for CodeEditSymbols resource declaration so its Bundle.module references compile. No repo-tracked dependency files were changed.