Mark the live claim on url finished (#1856): the implementation's branch
is ready to collect. The claim stays (with its expiry extended to at least
a week) until it is released or expires, so the action menu can offer
"Collect finished implementations" and search keeps skipping the issue.
With session, a claim another session holds is refused rather than
finished on its behalf.
Work claims (#1856, #1852): record, finish, release and list in-flight implementations and PR work.