// Package health provides a concurrent health check HTTP handler.
//
// The handler runs all registered checks in parallel, collects results within
// a configurable timeout, and returns a structured JSON response. It maps
// directly onto Kubernetes liveness and readiness probes.
//
// Components register themselves by implementing
// [observability.Checkable] from einherjar/contracts — no adapter needed.
//
//   - [observability.LevelCritical]: if DOWN, overall status is DOWN (503)
//   - [observability.LevelDegraded]: if DOWN, overall status is DEGRADED (200)
//
// # Example
//
//	srv.Get("/health", health.NewHandler(logger, db, cache, storage))
//
// Or with custom timeout:
//
//	srv.Get("/health", health.NewHandlerWithConfig(logger,
//	    health.Config{CheckTimeout: 3 * time.Second},
//	    db, cache,
//	))
package health