The contracts leaf of the codometer toolchain. It holds what a measurement
produces — the per-language statistics groups, the report vocabulary a
consumer joins across runs, and the errors a configuration is refused with —
and nothing that runs.
No service and no NestJS module lives here, which is what makes it a leaf every
other codometer package may reach without dragging a container behind it. The
test that decides whether a declaration belongs here is sharp: a type the tool
produces is core, and a value somebody writes in codometer.config.ts is
configuration.
