Constant NO_SHAPE_ID 

pub const NO_SHAPE_ID: u32 = u32::MAX; // 4_294_967_295u32

Sentinel shape_id for records constructed outside an Op::MakeRecord site (#462 slice 2). Program::record_shapes is bounded by u32::MAX - 1 in practice (each compile-time record literal adds one entry), so reserving the top of the u32 range as “no shape” keeps Value::Record.shape_id a flat u32 — the Op::GetField IC’s hot path is a single u32 compare, no Option discriminant.