Function link_transfer 

pub fn link_transfer(
    vault_path: &Path,
    pp: &Passphrase,
    out_ref: &str,
    target: TransferTarget,
    now: OffsetDateTime,
) -> Result<EventId, CliError>

FR6/TP7: confirm a self-transfer. target is a destination TransferIn event (--to-event) or a known wallet (--to-wallet); the engine relocates the lots carrying basis + acquired_at.