Round-ready email says "All 1 change is done" when a round has one comment

[Test bug filed by Claude to try the bug agent]

When a round has exactly one comment and it's marked Fixed, the "ready for review" email and the Slack/webhook message read "All 1 change is done. Have a look" (subject: "All 1 change is done — have a look at [project name]"). It should read naturally, e.g. "The change is done" or "1 change is done".

Steps:

1. Create a website review and add a client email in Project details.
2. As the client, open the review link, add one comment and press Send my feedback.
3. In the studio, set that comment to Fixed and press Ready for review → Start the next round.
4. Look at the email subject and heading the client gets (or the Slack/webhook text).

Expected: natural copy for a single change.
Actual: "All 1 change is done".

Where: lib/rounds.ts digestLine(); lib/db-rounds.test.ts currently asserts the awkward wording. Seen on the admin-upgrade branch, any browser (it's server-side copy).