argus: add Phase 1 active monitoring system
- What: alerting.py (7 health checks), alerting_routes.py (3 endpoints),
PATCH_INSTRUCTIONS.md (app.py integration guide for Rhea)
- Why: engineering acceleration initiative — move from passive dashboard
to active monitoring with agent health, quality regression, throughput
anomaly, stuck loop, cost spike, and domain rejection pattern detection
- Endpoints: GET /check, GET /api/alerts, GET /api/failure-report/{agent}
- Deploy: Rhea applies PATCH_INSTRUCTIONS to live app.py, restarts service,
adds 5-min systemd timer for /check
Pentagon-Agent: Argus <9aa57086-bee9-461b-ae26-dfe5809820a8>