Interface ReadinessRegistrar

Passed to adapter builders via BuilderContext.readiness. Builders that open a connection SHOULD register a probe for it:

ctx.readiness?.register({ name: "redis", check: () => client.ping() })

Mirrors LifecycleRegistrar: the boot planner owns the instance and seeds it as the readinessRegistrar bootstrap component, so a builder reached through a module that declares optional: ["readinessRegistrar"] receives it. Always use optional chaining — a factory constructed outside the boot planner (unit tests) receives {} as its context.