Export app code as a zip

Download any owned commit as a time-limited zip (Pro, owner-only).

Export one version

1. Run export_code {app, sha?}; sha defaults to main.
2. Require the owner’s Pro plan; Free accounts get payment_required.
3. Download from the returned url with its sha, bytes, and expires_at.
4. Expect the zip to hold exactly the committed tree under <slug>-<shortsha>/.
5. Stay under 256 MiB; larger trees refuse with a clear error.
6. Download within 1 hour; the stored object is deleted after 24 hours.

For the person-side walkthrough, see How deploys work.