A running check is named on its pull: the checks line says 'Check running · 12 min' and links to the run, titled 'Check of <sha> for #<pull>' #2279

First half of #1123. The owner could not find a forty-minute check that was running on his own pull.

Done looks like:

• [ ] While a check runs, the pull page's checks line reads "Check running · <age>" and links to the check's run. Afterwards it reads "Check passed in <duration>" or "Check failed: <first failing case>". It never calls a check a deploy.
• [ ] A check's run page is titled "Check of <short sha> for #<pull>".
• [ ] Tests in a file listed in GATE cover the running line, its link, the finished lines and the run page title.

Files: the pull page under src/web/pages/, and src/checks/summary.ts.