//! Module: db::session::sql::projection::contract
//! Responsibility: carry outward SQL projection labels and display scales.
//! Does not own: projection execution, prepared-plan cache state, or payload
//! assembly.
//! Boundary: keeps the session SQL result contract with the projection helpers
//! that derive it.
///
/// SqlProjectionContract
///
/// SqlProjectionContract is the outward SQL projection contract derived from
/// one shared lower prepared plan. SQL execution keeps this wrapper so
/// statement shaping stays owner-local while prepared-plan reuse lives below it.
///
pub