test(good-fences): the model counts the rs in strawberry (red)

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>

good-fences/itest/model.test.ts

@@ -0,0 +1,16 @@
+/** @file The model, called for real through the Workers AI binding. */
+import { env } from "cloudflare:workers";
+import { expect, test } from "vitest";
+
+import { makeWorkersAiModel, MODEL } from "../src/model.ts";
+
+test("the model counts the rs in strawberry", async () => {
+	const model = makeWorkersAiModel(env.AI, MODEL);
+	const reply = await model.complete([
+		{
+			role: "user",
+			content: 'How many times does the letter r appear in "strawberry"? Answer with just the number.',
+		},
+	]);
+	expect(reply.trim()).toMatch(/^3\b/);
+});