Unit tests for checkHardReview and checkMilestone10 #91

What

checkHardReview and checkMilestone10 in lib/pr-journey.ts encode milestone 9 (3+ review rounds or closed) and milestone 10 (must be merged).

There are no tests for it yet.

Cover at least

• milestone 9: closed with 0 rounds passes, open with 3 rounds passes, merged with 2 rounds throws
• the milestone 9 error message includes the actual round count
• milestone 10: merged passes, open throws, closed throws

How

• Create lib/pr-journey.test.ts next to the code. Follow the style of lib/github-auth.test.ts.
• Run npm test. Then break the code on purpose (flip a condition) and watch at least one of your tests fail. Paste that failure output in the PR description, then undo the break.
• Test behaviour through the exported function only. Don't change the source file unless you find a bug, and if you do, stop and comment on this issue first.

Size: ~30–60 lines of tests, 0 lines of source.

Taking this? Comment /assign and the bot assigns you if it's free. One issue per person at a time; comment /unassign to hand it back. That's milestone 2 of the 10 PR Journey. Setup, the checks CI runs, and how to open the PR from your fork are in CONTRIBUTING.md. Put Fixes #<this issue> in your PR description.