contracts is a synonym for the smart-contracts tag.
We have the following discussion: Should we blacklist the smart-contracts tag?
The tags contract-design, contract-development, contract-invocation and contract-debugging should jointly cover most usage.
All uses of the smart-contracts tag are retagged. Now we need to figure out what to do with the contracts synonym and smart-contracts itself.
If we decide we'd like to do the same for contracts, the process is we need this separate question for it.