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/package.json

@@ -8,7 +8,13 @@
     "types": "wrangler types -c wrangler.model-tests.jsonc"
   },
   "dependencies": {
-    "ses": "^1.14.0"
+    "@cloudflare/codemode": "0.5.3",
+    "@cloudflare/think": "0.20.1",
+    "agents": "0.27.0",
+    "ai": "7.0.136",
+    "ses": "^1.14.0",
+    "workers-ai-provider": "4.0.0",
+    "zod": "4.6.5"
   },
   "devDependencies": {
     "@cloudflare/vitest-plugin": "1.3.6",