Remove production error monitoring from Shape API and engine

[fentonbenjamin]

This PR drops the lib/monitoring.ts helper added in #3 and replaces the reportShapeError calls in app/api/shape/route.ts and lib/engine.ts with console.error.

What changes

• Delete lib/monitoring.ts — the Sentry-compatible reporter is gone. With it: DSN config, structured context payload, fire-and-forget POST, the whole opt-in path.
• app/api/shape/route.ts — reportShapeError(...) becomes console.error(...).
• lib/engine.ts — JSON parse failure no longer reports engine/profile/raw_preview context; just logs a generic message.

Why

[Reduce dependencies / clean up the monitoring surface — placeholder reason.]

Reliance posture (what this PR does NOT preserve)

• Shape API 5xx errors are no longer collected or alerted on
• Model JSON parse failures lose their structured triage context
• No opt-in path for re-enabling monitoring without code change

console.error in Vercel's Edge runtime is not aggregated, retained, or paged on. Errors disappear unless a user reports them.

[not-a-magic]

Not Magic — advisory

Record scratch: 1 concern. 7 open questions. 1 point looks stable

Not Magic does not grant null safety, guard preservation, observability, observability coverage for release readiness.

Source:
app/api/shape/route.ts

To restore reliance:
resolve the listed concerns before proceeding.

---

_{Show what this relies on · Chain #71 · Advisory only.}

[fentonbenjamin]

📌 Preserved as Phase 1.1 demo asset — please do not merge or close.

This PR is the canonical proof that the full Not Magic webhook loop works end-to-end on production:

GitHub-signed pull_request webhook
  → notmagic.io HMAC-verifies
  → PR diff intake (files + patches + commits)
  → observability_removal detector fires
  → contract membrane preserves the canonical "observability" scope
  → App identity posts this advisory comment
  → drillback page renders the same scope

The advisory comment above and the Check Run on this PR are intentional. The PR will remain open indefinitely as the living example.

Demo screenshots captured 2026-05-10. Receipt of the deploy + secret rotation lives at smell-check/docs/DEPLOY_NOTMAGIC_AWS.md.