/**
 * Resolve the "age" of a context-tree document for the visible recall summary.
 *
 * Resolution order, falling through on any failure:
 *   1. Frontmatter `updatedAt`   — standard topic files (post-curate timestamp)
 *   2. Frontmatter `synthesized_at` — synthesis files produced by `brv dream`
 *   3. Frontmatter `createdAt`   — older standard files that lack updatedAt
 *   4. File `mtime`              — last resort for files without timestamp frontmatter
 *   5. `undefined`               — file missing or path is a cross-project shared source
 *
 * Cross-project paths in the form `[alias]:relative/path.md` are not resolved here —
 * they live in another project's `.brv/context-tree/`, which the plugin does not see.
 */
export declare function resolveContextTreeAge(projectRoot: string, relativePath: string): Date | undefined;