feat(KB-070): add Ayu and One Dark themes to dashboard

- Add Ayu and One Dark to COLOR_THEMES and validThemes arrays
- Add CSS theme variables for both themes in styles.css
- Update ThemeSelector UI to include new theme options
- Extend Theme type to include ayu and one-dark values
- Update tests for ThemeSelector and useTheme hooks
- Add changeset for minor version bump

packages/core/src/types.ts

@@ -19,6 +19,8 @@ export const COLOR_THEMES = [
   "monochrome",
   "high-contrast",
   "solarized",
+  "ayu",
+  "one-dark",
 ] as const;
 export type ColorTheme = (typeof COLOR_THEMES)[number];