test(good-fences): lent a mower, a Think agent mows (red)

The first end-to-end test: a Project Think agent, on the real model,
writes code that runs in a dynamic worker and drives a mower; the test
counts the cells cut, and saves the turn to itest-output/.

Installs @cloudflare/think, @cloudflare/codemode, agents, ai,
workers-ai-provider, zod. The model-test worker now has a main entry,
the Neighbor DO, and a LOADER binding.

Red: src/worker.ts doesn't exist yet.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

good-fences/itest/neighbor.test.ts

@@ -0,0 +1,13 @@
+/** @file A Think agent, lent a mower, mows: model, generated code, sandbox, mower. */
+import { getAgentByName } from "agents";
+import { env } from "cloudflare:workers";
+import { expect, test } from "vitest";
+
+test("lent a mower, the neighbor mows", async ({ annotate }) => {
+	const neighbor = await getAgentByName(env.Neighbor, "weekend");
+	const turn = await neighbor.runTurn({ input: "you can use this mower for the weekend" });
+	await annotate("the turn", { body: JSON.stringify(turn, null, 2), contentType: "application/json" });
+
+	const cells = await neighbor.cutCells();
+	expect(cells.length).toBeGreaterThan(10);
+});