Fix OT when two adjacent paragraphs are merged backwards

Transforms were not ensuring a consistent style name was applied to the merged paragraph on all clients.

Incidentally... this issue was found when playing with the split screen editor!
To clarify a bit more, on each client, two paragraphs are combined into one.
So op 1 merges B into A, and op 2 merges C into B. This adjustment here accounts for this on each client.