Surface honesty on stderr — notices, warnings, and the zero-trade walk-forward
Two ways the release binary reports in a form that misleads a reader or a CI grep. #278 (observed in the campaign-scaling wake, #251; per-invocation counts raised further by the parallel cell loop, #277): benign gate-emptied notices and genuine per-cell faults share one undifferentiated aura: cell ... stderr idiom, so a real fault drowns among expected null-result notices. #313 (2026-07-22 external field test, triage: #314): a walk-forward whose 184 of 184 out-of-sample windows recorded zero trades completed indistinguishably from honest success, and downstream conclusions were drawn from an all-zero metrics table. The order is forced by #313's own deferral: #278 settles the stable, machine-separable marker scheme for the two stderr classes; #313's campaign-end all-zero-trades notice then slots into that scheme — the reverse order would decide the stderr format twice.
Done: the two stderr classes are visually and grep-separably distinct, and a walk-forward that never traded announces itself.
