bad error message: provenance

```
File "./fmdeps/cpp2v-core/rocq-bluerock-prelude/theories/elpi/derive_test.v", line 18, characters 4-192:
Error:
Incompatible provenance for symbol main: Ast.Structured.Elpi != (Ast.Structured.OCaml Ast.Structured.Builtin {variant = 0})
```
because they are redeclaring the type of `main` without `:external`