feat(eval): add evidence pipeline acceptance closure

mvp/eval/README.md

@@ -29,18 +29,21 @@ The baseline evaluates saved trace fixtures. It does not start the application a
 The committed baseline currently contains:
 
 ```text
-8 fixed cases
-8 passing fixture evaluations
-2 PASS verdicts
+10 fixed cases
+10 passing fixture evaluations
+4 PASS verdicts
 5 LOW_CONFID verdicts
 1 REJECT verdict
 ```
 
-The three V2 audit-closure cases cover:
+The V2 evidence-pipeline matrix covers:
 
+- Positive supported evidence for a narrow HighCPU observation.
+- No-evidence `negative_observation` using `$.no_evidence`.
 - Gatekeeper failure for a fabricated tool invocation reference.
 - Unsupported claim filtering before the final answer.
 - Composer fallback rendering without raw Executor JSON leakage.
+- Gatekeeper rule set version audit for new matrix fixtures.
 
 ## Verification
 
@@ -76,6 +79,7 @@ Stage 5 adds these V2 checks:
 - Required V2 fixtures must include `gatekeeper_result`, `claim_checks`, and `composer_output`.
 - `claim_checks` must be structurally auditable.
 - Composer output must record whether normal parsing or fallback rendering was used.
+- Gatekeeper rule set version can be asserted per fixture.
 - Final answers must not leak raw Executor protocol markers such as `executor_evidence_v2`, `answer_version`, `evidence_bindings`, or `claim_id`.
 - Configured unsupported claim keywords must not appear as confirmed final-answer content.