docs(wiki): add Startup Lifecycle & Readiness (v1.221.0) New operator page documenting the 14 journal-visible startup lifecycle phases, the systemd-vs-direct-run readiness contract (ready_sent vs ready_attempted, bound-socket != ready), the one-shot startup-pending diagnostic, the additive lifecycle status IPC object, degradable components, and child systemd-notify isolation, plus a troubleshooting runbook. Carries an unreleased banner (merged for upcoming v1.221.0; not in v1.220.10). Sidebar + cross-links from Systemd Units and Troubleshooting.