"the card lists the parent's commits > 12 commits show 10 and 'and 2 more'" passes every time on a loaded check machine #5672

Done:

• [ ] bun test --rerun-each 30 test/spawn-upstream-card.test.ts -t "12 commits show 10" passes, and the pull names the cause it found. A likely lead: commit times or order that tie under load; give the fixture's commits distinct, fixed timestamps.
• [ ] Nothing the test promises is weakened: no retries, no dropped assertion, no longer timeouts.
• [ ] If the cause is in the product (the card's commits unordered on equal times, say), fix the product and say so.

Files: test/spawn-upstream-card.test.ts and the module the cause is in. Why now: it sank #3309's second try (pull #5669), which only touched the person page.