Eval-core

Add a new scorer to EvalCore (a new `type:` under `scorers:` in evals.yaml). Follow this checklist so config schema, implementation, factory, tests, and docs stay in sync.

Add a new target type to EvalCore (a new `type:` under `targets:` in evals.yaml), e.g. a provider adapter or transport. Follow this checklist so schema, adapter, factory, and wiremock tests stay in sync.

Verify EvalCore end-to-end — format check, clippy, full test suite, and a real CLI run against the quickstart example. Use before declaring any change done, before commits, and after dependency or toolchain changes.