v2.5.0: lifecycle failure handling

What's changed

• Define lifecycle failure boundaries: empty Run now panics, and component errors include component names while preserving errors.Is.
• Add configurable shutdown timeouts through WithShutdownTimeout and ErrShutdownTimeout.
• Preserve and join independent input, readiness, component, cleanup, and timeout errors without propagated cancellation noise or duplicate causes.
• Distinguish successful probe(nil) from readiness failures wrapping context.Canceled.
• Release lifecycle listeners and signal handlers, and simplify parent-readiness coordination.

Pull requests

• #13
• #14