Nuxt Ui Guideline: Color Mode — Use UColorModeButton for theme toggle. Description: Built-in light/dark mode toggle button. Do: UColorModeButton component. Don't: Manual color mode logic. Good Example: <UColorModeButton/>. Bad Example: <button @click="toggleColorMode">. Severity: Low. Docs: https://ui.nuxt.com/docs/components/color-mode-button.