Review on #136434 (@jquesnelle): discover() sorted records by version only,
so attempts inside a version kept git ls-remote's NAME order (rc.10 between
rc.1 and rc.2). reconcile indexes records by version with the last one
winning, so once a version reached rc.10 it handed rc.9 (burned, no release)
to publish_attempt, which refuses with "Final tag release database ID is
invalid". v0.21.7 is at rc.9, so its next cut is exactly rc.10.
- Sort by (version, attempt).
- The test fakes list refs sorted by name, as git does; insertion order hid this.
- rc.10 test (fails without the sort), and a same-commit retry test (rc.1
abandoned, rc.2 re-cut at the same commit wins).