Nuxt Ui Guideline: Color Mode — Use UColorModeSelect for theme picker. Description: Dropdown to select system light or dark mode. Do: UColorModeSelect component. Don't: Custom select for theme. Good Example: <UColorModeSelect/>. Bad Example: <USelect v-model="colorMode" :items="modes"/>. Severity: Low. Docs: https://ui.nuxt.com/docs/components/color-mode-select.