feat: deliver v1.8.0 harness reliability and parity updates

skills/eval-harness/SKILL.md

@@ -234,3 +234,37 @@ Capability: 5/5 passed (pass@3: 100%)
 Regression: 3/3 passed (pass^3: 100%)
 Status: SHIP IT
 ```
+
+## Product Evals (v1.8)
+
+Use product evals when behavior quality cannot be captured by unit tests alone.
+
+### Grader Types
+
+1. Code grader (deterministic assertions)
+2. Rule grader (regex/schema constraints)
+3. Model grader (LLM-as-judge rubric)
+4. Human grader (manual adjudication for ambiguous outputs)
+
+### pass@k Guidance
+
+- `pass@1`: direct reliability
+- `pass@3`: practical reliability under controlled retries
+- `pass^3`: stability test (all 3 runs must pass)
+
+Recommended thresholds:
+- Capability evals: pass@3 >= 0.90
+- Regression evals: pass^3 = 1.00 for release-critical paths
+
+### Eval Anti-Patterns
+
+- Overfitting prompts to known eval examples
+- Measuring only happy-path outputs
+- Ignoring cost and latency drift while chasing pass rates
+- Allowing flaky graders in release gates
+
+### Minimal Eval Artifact Layout
+
+- `.claude/evals/<feature>.md` definition
+- `.claude/evals/<feature>.log` run history
+- `docs/releases/<version>/eval-summary.md` release snapshot