A first integration test of the model call: Workers AI through the AI binding, behind the same `complete(messages)` interface as the sim's fake model. Opt-in (`pnpm test:model`) since it needs `wrangler login` and costs money. Red: src/model.ts doesn't exist yet. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>