Behaviour-preserving removal of the unreachable single-run cost seam: no
caller ever passed Some(cost). Drops the cost parameter from wrap_r (the
compiler enumerated 8 sites, all passing None), the dead branch, the
vol_proxy arm, CostConfig, SLIP_VOL_LENGTH, and the 4 inert cost imports;
RollingMax/RollingMin/Sub move to #[cfg(test)] (last production caller
gone). The cost_graph composite stays alive in aura-composites; the
campaign/sweep reduce path (C10) is untouched. Decision + rationale on the
issue. Suite green unchanged (62 groups), clippy clean.
closes#221
Brummel
b5ad53d233