First fieldtest of the sum combinators. A standalone downstream-consumer crate
(fieldtests/cycle-0008-sum-combinators/) path-depends on the engine crates and
exercises the post-0008 surface from the public interface only (rustdoc + ledger
+ glossary + project-layout, never crates/*/src).
Primary axis empirically met: the north-star two-signal combine move now uses the
shipped Add (Add::new() dropped in exactly where the 0007 fixture hand-authored
an Add2) — the 0007 boilerplate is retired, end to end through SimBroker to a
deterministic recorded pip curve.
Findings: 0 bugs, 1 friction, 2 spec_gaps, 3 working.
- working ×3: Add2 retired; LinComb weighted/variadic sums exact (<1e-12);
warm-up barrier + empty-weights panic as documented.
- spec_gap: Add/LinComb per-input firing policy (Firing::Any / mode-A as-of
join) absent from the public surface — same class as the 0007 SimBroker gap.
- spec_gap: a fired combinator emits one row per *cycle*, so a heterogeneous
same-timestamp multi-source trace can carry >1 row per timestamp (correct per
C4/C5, undocumented at this surface).
- friction: nested consumer crate still needs the empty [workspace] table
(carried from 0006/0007; #9 closed the docs half; folds into aura new).
Spec feeds the next plan as reference.
