Produces a cross-incident trend analysis for a time period — period summary vs prior period, recurring root-cause patterns with evidence, a per-service fragility breakdown, a preventability percentage, action-item follow-through, the top 3 systemic reliability investments, and metrics to track next period. Use when the user says "analyze our incidents this quarter", "incident trends", "reliability review", or pastes a list of incidents with root causes. Use this for systemic patterns across many incidents, not for a single incident's postmortem (planning/incident-postmortem) or live response.
