Function open_stores_for_preview 

fn open_stores_for_preview(
    shared_store_path: &Path,
    data_dir: &Path,
) -> Result<(Store, Option<Store>), String>

Open the shared + channel stores the way every writer does (creating the channel dir/db on a fresh install — see the comment inside). Shared by the locked batch and the lock-free --list/--dry-run previews.