fix: support named colors and single-mode theme imports (v1.2.1)

[kkugot]

Summary

Fix theme import/export handling so named CSS colors and dark-only or light-only theme bundles can be released safely.

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Context / Motivation

Importing some valid OpenCode themes failed because named colors like teal were not normalized and single-mode theme files were rejected unless every token declared both dark and light values.

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Changes

• add CSS named color normalization in the app and import script
• accept combined theme token objects that provide dark, light, or both
• merge partial JSON mode updates without overwriting the untouched mode
• add regression coverage for named colors, dark-only imports, and light-only imports
• bump the package version to 1.2.1

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Testing

• ✅ npm run test
• ✅ npm run lint
• ✅ npm run build
• ✅ verified public/import-export.sh with dark-only and light-only named-color theme files

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Version

Patch release: 1.2.1