LlmBoot4HealthIndicator

The Spring Boot 4 health indicator, registered by LlmBoot4ActuatorAutoConfiguration. Spring Boot 4 moved HealthIndicator and Health from org.springframework.boot.actuate.health (spring-boot-actuator) to org.springframework.boot.health.contributor (spring-boot-health), so the Boot 3 LlmHealthIndicator cannot be one; this reports exactly what it does, from the same probe, settings and cache rules.