feat: expose Phase 2 features via CLI

- Add agent CLI commands: simctl agents list/run
- Implement IAM analyzer agent with privilege escalation detection
- Add multi-vantage system with 4 attack perspectives
- Create agent registry with automatic discovery
- Add comprehensive documentation for Phase 2 features

New commands:
- simctl agents list: List registered security agents
- simctl agents run: Run specific agent with vantage control

Features exposed:
- IAM Policy Analyzer with privilege escalation detection
- Multi-vantage contexts (external, internal, iam-restricted, physical)
- Agent registry with automatic discovery
- Vantage-aware agent execution

Documentation added:
- docs/guides/IAM-ANALYZER-USAGE.md: Complete IAM analyzer guide
- docs/guides/MULTI-VANTAGE-USAGE.md: Multi-vantage system guide
- Updated STATUS.md: Phase 2 marked as complete
- Updated README.md: Added Phase 2 features to capabilities
- Updated CHANGELOG.md: Added Phase 2 features to v0.3.0

Implements: Phase 2 Features Exposure
Status: Complete ✅