Module undo 

Purpose: Provide the public undo API for queue snapshot creation, listing, restore, and retention.

Responsibilities:

• Declare the undo child modules.
• Re-export the stable undo data models and operations.

Scope:

• Thin facade only; implementation lives in sibling files under undo/.

Usage:

• Import undo helpers through crate::undo.

Invariants/Assumptions:

• The public undo API remains stable across this split.
• Snapshot creation, restore, and pruning behavior remain unchanged.

Structs

RestoreResult

Result of a restore operation.

SnapshotList

Result of listing snapshots.

UndoSnapshot

Full snapshot content (stored in JSON file).

UndoSnapshotMeta

Metadata about a single undo snapshot.

Functions

create_undo_snapshot

Create a snapshot before a mutation operation.

list_undo_snapshots

List available undo snapshots, newest first.

load_undo_snapshot

Load a full snapshot by ID.

prune_old_undo_snapshots

Prune old snapshots to enforce retention limit.

restore_from_snapshot

Restore queue state from a snapshot.

undo_cache_dir

Get the undo cache directory path.