Schema diff → migrations bot

on:
  pull_request:
    paths: ['prisma/schema.prisma']
jobs:
  migrate:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with: { fetch-depth: 0 }
      - uses: claudeloops/action@v1
        with: { locker: migrations, agent: .claude/agents/migrate.md, model: claude-opus-4 }

# Migration generator

Rules:
- Add columns nullable, backfill, then set NOT NULL in a separate migration.
- For renames: add new column, dual-write, backfill, drop old later.
- Indexes on tables > 1M rows: use `CREATE INDEX CONCURRENTLY` and skip the implicit lock.
- Always emit `down.sql`.
- Output a `DESTRUCTIVE_OPS.md` listing every drop or rename with a 'Safe? Y/N' header.