Code mode (2c): the harness turns what I say plus `about` into a prompt;
the model replies with `(env) => ...` code. Checked textually for now,
since workerd won't eval it: the code pushes `env.mower` and calls only
methods in `about`. It also prints the code, to see what the model writes.
Red: src/code-mode.ts doesn't exist yet.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
