02-use-cases - [Content Improvement] IT Incident Response Agent: streaming, observability, and production-ready docs

**Please list the sample in which the bug is present.**

02-use-cases/02-workflow-automation-agents/it-incident-response-agent

**Improvement Description**

Enhance the IT Incident Response Agent to improve production-readiness and demo-quality:

* Real-time streaming of pipeline stages and evaluation results
* Agent robustness fixes (entrypoint validation, memory cross-session retrieval, DynamoDB serialization)
* OTEL observability improvements (span attributes, tool-call hooks, e2e test spans)
* Expanded README with architecture diagrams, prerequisites, usage, sample prompts, and cleanup steps
* Architecture documentation (docs/ARCHITECTURE.md)
* Demo GIF for quick visual reference

(PR Fast Follow)