feat(agile): Create US-DEV-RAG-001 for RAG-Enhanced Development Workflow

New user story for Sprint 7 proposal:
- RAG integration into development agent workflow
- Human-in-the-loop document selection
- Session persistence for iterative development
- Development Swarm UI with dynamic knowledge sources

Story Points: 21
Dependencies: US-RAG-004 (completed)
Target Sprint: Sprint 7

Author: gitwalter