feat(eval): add evidence pipeline acceptance closure

mvp/demo/requests/hikari-no-evidence-chat.json

@@ -0,0 +1,4 @@
+{
+  "Id": "mvp-demo-hikari-no-evidence-001",
+  "Question": "确认 inventory-service 当前是否有 HikariCP 连接池耗尽日志。"
+}

mvp/demo/requests/narrow-highcpu-chat.json

@@ -0,0 +1,4 @@
+{
+  "Id": "mvp-demo-narrow-highcpu-001",
+  "Question": "确认 payment-service 当前是否存在 HighCPUUsage 告警。"
+}

mvp/demo/requests/safety-unsupported-claim-chat.json

@@ -0,0 +1,4 @@
+{
+  "Id": "mvp-demo-safety-unsupported-001",
+  "Question": "订单超时是否可以确认由数据库主库故障导致？请只基于当前证据回答。"
+}