Implements the HealthMonitor class for tracking connection health:
- Tracks connection states per stream (active, stale, disconnected)
- Records events and calculates throughput (events/second)
- Detects stale streams (no events for configurable threshold)
- Exposes Prometheus-compatible metrics endpoint (/metrics)
- Provides HTTP health endpoints (/health, /ready, /live)
Exports: HealthMonitor, HealthReport, HealthStatus, StreamHealth, StreamStatus
Tests: 47 comprehensive unit tests covering all functionality
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>