The floor tag marks what has already been released, so tagging the
commit being pushed leaves nothing between the floor and HEAD --
semantic-release then correctly reports there is nothing to release.
That is what the first run did: it seeded v0.0.0 on the merge commit
itself and cut no release.
HEAD^ is the first parent, so on a merge commit it is main as it was
before the merge and everything the merge brought in is releasable.
The tag has been moved to 6fb7b5e by hand; this is so the next repo
never needs that.