Write a blameless post-mortem document

Write a blameless post-mortem document for the following incident.

Incident summary:
{{what broke, what users experienced, how long it lasted}}

Timeline (rough notes are fine):
{{chronological notes — when detected, actions taken, when resolved}}

Contributing factors you've identified:
{{e.g. no alerting on X, manual deploy step, config drift, cascading failure}}

The document should include:
1. **Summary** — 3 sentences: what broke, user impact, total duration
2. **Timeline** — chronological, times in UTC, focus on decision points not every action
3. **Root cause** — layered analysis: trigger → proximate cause → systemic reason
4. **Contributing factors** — what made the root cause possible or worse
5. **Impact** — affected users, services, data, and duration
6. **What went well** — detection speed, communication, tooling that helped
7. **Action items** — table: Priority | Action | Owner | Deadline — weight systemic fixes over one-off patches

Tone: blameless, factual, forward-looking. Avoid naming individuals as causes. Focus on systems and processes.