RnD openDerivation/godbolt: compare the HAPI wave4 cell with the same cell in plain C

.RnD/openDerivation/README.md

@@ -97,7 +97,7 @@ that does everything and writes its logs next to it (`log.txt`, and `log/` for r
 | `round1/` | one closed composition over one open class and a terminal; bare use must not compile; the alias form must be refused | `round1/run.sh` |
 | `round2/` | static_net's `waveCell.h` / `linCell.h` in `:` syntax (`src/`, `Cell` closed with `final API`), translated (`out/include/`); round trip (diff = the `Cell` lines only); `check/build.sh` unchanged; `compare_emlearn` and `measure/` in simavr; `avr-objdump` of 27 AVR programs; the struct `Cell` next to `hapi::APIOf` | `round2/run.sh` (a few minutes) |
 | `round2/variants/` | `hapi::APIOf` itself written in `:` syntax | `round2/variants/run.sh` |
-| `godbolt/` | Banknote wave4 for Compiler Explorer, in the `:` form (translated) and the original `APIOf` form, including `single/hapi.h` by pinned raw URL; `verify.sh` checks both give static_net's `bnc_predict` | `godbolt/verify.sh` |
+| `godbolt/` | Banknote wave4 for Compiler Explorer: the HAPI `APIOf` cell against the same cell in plain C (28 vs 27 instructions, one register copy apart), plus the `:` form (translated), all including `single/hapi.h` by pinned raw URL; `verify.sh` checks the two HAPI forms give static_net's `bnc_predict` and the plain C gives the same answers on all 2^32 inputs | `godbolt/verify.sh` |
 | `round3/` | coverage: components and closing on a user terminal, base-clause chains and folds, named compositions against their plain-C++ equivalent, constructors, rule-1 rebinding, family/statics, nominal identity (incl. across TUs), `super` precedence, dependence, component `rules()`, XXXDef `Expand` entries (a Def nested in an outer rule walk; Defs in the global, `a::b`, inline and anonymous namespaces; the nested-class warning), a type named `final` as terminal and as layer, duplicate layers, the label hazard, closed classes as layers (a data-only mixin, statics per family member, bare use still working); 15 translator refusals; 16 compiler rejections | `round3/run.sh` |
 
 Round 2 runs `build.sh` "unchanged" by building two throwaway mirrors of `examples/static_net`: `check/`, `compare_emlearn/`