Brummel
1a33b4f252
Four tasks for the behaviour-preserving carrier swap: (1) add the branch-free AnyColumn::push_cell + round-trip test (additive); (2) the atomic lib-code flip (Node::eval -> Option<&[Cell]>, 8 aura-std nodes, recorder, harness forward loop) gated by a lib-only build; (3) the cfg(test) migration (fixtures + eval-output assertions per the spec's three-role rule) gated by the full four-gate run; (4) the C7/C8 ledger realization note. refs #74