Add docker-compose integration test harness

[codefather2026]

Summary

Added a docker-compose-based integration test harness for Wraith that runs against a real Postgres instance, seeds representative fixtures, and exercises live API endpoints through Vitest. Also wired the suite into CI so it runs on every pull request.

Related issue

Type of change

• Bug fix
• New feature
• Refactor
• Docs
• Tests
• CI / tooling

Checklist

• I have read CONTRIBUTING.md
• npx tsc --noEmit passes
• npm run build passes
• I added / updated tests where relevant
• I updated docs where relevant

[Miracle656]

Thanks for this. A few things to resolve before it can land:

1. The Integration tests job is failing — Cannot find module '@rolldown/binding-linux-x64-gnu' (the npm optional-deps bug, npm/cli#4828). The committed package-lock.json doesn't include the Linux native binding Vitest needs in CI. Regenerating the lockfile so the platform-optional deps are captured (or pinning the binding) should fix it.

2. Overlap with the existing harness. main already has a docker-compose integration setup (from #65). Please clarify what this adds on top of it — if it's an improvement, ideally extend the existing harness rather than adding a parallel vitest.integration.config.ts path; if it supersedes #65's, say so explicitly.

3. Unrelated change: src/__tests__/opa.test.ts and the src/index.ts edit don't look related to an integration harness — if they belong to a different concern, please split them out.

Once the integration job is green and the relationship to the existing harness is clear, I'll re-review. Thanks!