harness-eval-contract

Add an evals.md section to the spec covering capability evals, regression evals, command evals with expected outputs, and Judge evals with a rubric and threshold. Implementation should not start until this eval contract is explicit.

It should include capability evals describing what must become possible, regression evals describing what must remain true with a covering test, command evals with exact checks and expected outputs, Judge evals with rubric and threshold, and an evidence location.

Citing agent-os/quality-thresholds.json as the single source prevents specs from hardcoding values that drift from the quality gate. When two documents restate thresholds independently, they eventually disagree about what passing means.

An eval contract is required for medium or high risk implementation work. Low risk changes may not need the full contract, but any bug fix must add a regression eval with a corresponding regression test.

The contract requires every bug fix to add a regression eval covered by a regression test. Without it, the fixed behavior has no guard against reintroduction and the spec's regression section remains incomplete.