Retire exercise_status: maturity is the only notion; add CLI tests (RBT-WP-0009-T01)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

Assistant: claude-code
Assistant-Model: sonnet
Assistant-Process: 295952@bnt-lap001
Assistant-Session: e93f64ad-516c-46eb-9666-aad8d300c477

runbooks/example-hello/pack.yaml

@@ -3,7 +3,6 @@ id: rtut.example-hello
 title: Example - check a host answers
 owner: runbook-tutorials
 outcome: You have proven a host answers on the network.
-exercise_status: exercised 2026-09-29 by Bernd
 engine: native
 parameters:
   - {id: host, label: Host name, type: string, default: localhost, pattern: "[a-zA-Z0-9.-]+"}