Phase 3: Cascade LLM Router with automatic failover

- YAML-based provider configuration (config/providers.yaml)
- Priority-ordered provider routing
- Circuit breaker pattern for failing providers
- Health check and availability monitoring
- Metrics tracking (latency, errors, success rates)
- Support for Ollama, OpenAI, Anthropic, AirLLM providers
- Automatic failover on rate limits or errors
- REST API endpoints for monitoring and control
- 41 comprehensive tests

API Endpoints:
- POST /api/v1/router/complete - Chat completion with failover
- GET /api/v1/router/status - Provider health status
- GET /api/v1/router/metrics - Detailed metrics
- GET /api/v1/router/providers - List all providers
- POST /api/v1/router/providers/{name}/control - Enable/disable/reset
- POST /api/v1/router/health-check - Run health checks
- GET /api/v1/router/config - View configuration

src/router/__init__.py

@@ -0,0 +1,12 @@
+"""Cascade LLM Router — Automatic failover between providers."""
+
+from .cascade import CascadeRouter, Provider, ProviderStatus, get_router
+from .api import router
+
+__all__ = [
+    "CascadeRouter",
+    "Provider",
+    "ProviderStatus",
+    "get_router",
+    "router",
+]