/**
 * Resolves `'auto'` against the document root the same way TxMarkdownView
 * does (data-theme attribute first, then light/dark classes), kept as a
 * composable so TxStreamMarkdown and its fenced-block renderers share one
 * observer instead of three.
 */
export declare function useAutoTheme(theme: () => 'light' | 'dark' | 'auto'): import('vue').ComputedRef<"dark" | "light">;