docs: add complete Epic 7 stories (Production-Grade Reliability)

Added all 7 stories for Epic 7:
- Story 7-1: Typed Error Handling
- Story 7-2: Structured Logging System
- Story 7-3: Performance Benchmarking (Event Sourcing)
- Story 7-4: Stress Testing and Fault Tolerance
- Story 7-5: Prometheus Metrics Export
- Story 7-6: EventHandler Interface (validated & fixed)
- Story 7-7: LogHandler Interface (validated & fixed)

Validation results:
- Story 7-6: 98.3% score, ready for dev (fixed typo & config)
- Story 7-7: 100% score, ready for dev (added perf metrics)

Epic 7 complete: All stories validated and ready for development
Updated: sprint-status.yaml

Author: zhaojing1987

docs/sprint-artifacts/7-1-typed-error-handling.md

@@ -113,14 +113,14 @@ development_status:
   epic-6-retrospective: optional
 
   # Epic 7: 生产级可靠性 (7 stories)
-  epic-7: backlog
-  7-1-typed-error-handling: backlog
-  7-2-structured-logging-system: backlog
-  7-3-performance-benchmarking: backlog
-  7-4-stress-testing-and-fault-tolerance: backlog
-  7-5-prometheus-metrics-export: backlog
-  7-6-eventhandler-interface: backlog
-  7-7-loghandler-interface: backlog
+  epic-7: in-progress
+  7-1-typed-error-handling: ready-for-dev  # ✅故事草稿完成,全面的类型化错误处理系统,RFC 7807集成,错误分类器优化,完成日期2026-01-07
+  7-2-structured-logging-system: ready-for-dev  # ✅故事草稿完成,结构化日志系统,敏感信息脱敏,上下文日志,动态级别配置,完成日期2026-01-07
+  7-3-performance-benchmarking: ready-for-dev  # ✅故事草稿完成,完整性能基准测试框架,API/DSL/Agent性能验证,基线系统,回归检测,完成日期2026-01-07
+  7-4-stress-testing-fault-tolerance: ready-for-dev  # ✅故事草稿完成,压力测试和容错验证,1000+并发,Event Sourcing零状态丢失,故障注入测试,资源泄漏检测,完成日期2026-01-07
+  7-5-prometheus-metrics-export: ready-for-dev  # ✅故事草稿完成,Prometheus指标导出,工作流/Agent/节点指标,Grafana Dashboard,监控系统完善,完成日期2026-01-07
+  7-6-eventhandler-interface: ready-for-dev  # ✅故事草稿完成,EventHandler接口实现,工作流生命周期事件,Webhook/Slack/自定义集成,异步非阻塞,完成日期2026-01-07
+  7-7-loghandler-interface: ready-for-dev  # ✅故事草稿完成,LogHandler接口实现,工作流执行日志收集,Stdout/File/Loki/Elasticsearch集成,批量缓冲优化,完成日期2026-01-07
   epic-7-retrospective: optional
 
   # Epic 8: 部署和运维 (5 stories)