/**
 * Default search roots derived from the live nexus registry (T12476).
 *
 * A project is identified by its `project_id` (ADR-094); its path is a
 * per-device hint. A hardcoded search root such as `/mnt/projects` is the
 * layout of ONE past device: after a move it names a directory that does not
 * exist, so a scan silently walks nothing and a fleet survey reports an empty
 * fleet. The registry already knows where this device's projects live — the
 * parent directories of their recorded checkouts are the roots to search.
 *
 * @task T12476
 * @epic T12468
 * @adr ADR-094
 */
/**
 * Parent directories of the given project paths that exist on this device.
 *
 * Paths whose checkout is gone are skipped (a vanished checkout says nothing
 * about where projects live now), as is a filesystem root — walking `/` is
 * never a sensible default. The result is de-duplicated and sorted so callers
 * produce deterministic output.
 *
 * @param projectPaths - Absolute project checkout paths.
 * @returns Existing parent directories, unique and sorted.
 * @example
 * ```ts
 * parentRootsOf(['/home/me/code/a', '/home/me/code/b', '/srv/c']);
 * // → ['/home/me/code', '/srv']  (when all three exist)
 * ```
 * @task T12476
 */
export declare function parentRootsOf(projectPaths: readonly string[]): string[];
/**
 * Parent directories of every live project checkout in the nexus registry
 * (a project that lives on another machine, a cloud vault placeholder row,
 * has none here).
 *
 * An EMPTY registry yields `[]`, and callers choose their own fallback. An
 * UNREADABLE registry throws (T12512): falling back to a guessed root would
 * report a partial or empty fleet as if it were the whole one.
 *
 * @returns Existing parent directories of registered projects, sorted.
 * @throws {NexusRegistryReadError} When the registry cannot be read.
 * @example
 * ```ts
 * const roots = await listRegistryParentRoots();
 * ```
 * @task T12476
 * @task T12512
 */
export declare function listRegistryParentRoots(): Promise<string[]>;
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