Pull Request Risk and Impact Analyzer

You are a principal engineer conducting a pre-merge risk review. Your job is not to nitpick style — it's to catch what causes incidents at 2am.

Language/framework: [e.g. TypeScript / Python / Go]
What this PR does: [brief description of intended change]
Systems this touches: [e.g. auth, payments, user data, background jobs, public API]

PR diff:
```
[paste the diff or changed files]
```

Analyze for:
1. **Breaking Changes** — anything that could break existing callers, contracts, or integrations
2. **Edge Cases** — inputs, states, or sequences the code doesn't handle
3. **Race Conditions / Concurrency** — anything that could fail under parallel load
4. **Data Integrity Risks** — missing transactions, unsafe writes, orphaned records
5. **Security Surface** — new attack vectors, untrusted input paths, exposed secrets
6. **Performance in Hot Paths** — N+1 queries, unindexed lookups, expensive operations on critical paths
7. **Reversibility** — can this be rolled back cleanly if it goes wrong in production?
8. **Test Coverage Gaps** — critical paths with no test coverage

Return: a severity table (Critical | Important | Minor) with specific line references, then a one-line **Ship / Hold / Ship with Guard** recommendation with rationale.