docs(agents): require update-behavior review and best-effort updates …

docs(agents): require update-behavior review and best-effort updates (#145100)

Peter's rule: openclaw update always finishes best effort; every change touching update, Doctor, service lifecycle, config/state migration or plugin loading states its first-hop behavior under shipped drivers and existing operator state; recoverable hiccups become warnings, backup before mutating, rollback restores, refuse only for concrete data at risk without leaving the Gateway stopped; timeouts derived from measured state and sized for old hardware. Context: the 2026.9.3/2026.9.4 update-failure campaign (25 root causes, half of them fail-closed admission against existing state, five fixed budgets sized on developer machines).