Fix forge lint "custom-errors"

Followup for #555

We prefer typed `error` over `Error(string)` because using strings significantly increases codesize. We also want to use such errors instead of naked reverts to provide informative feedback to help with debugging such errors.

Start by reading the follow-up context in issue #555, then run Forge's custom-errors lint to identify the affected contracts and reverts. Done means the reported violations use typed errors instead of Error(string) or naked reverts, while preserving informative debugging feedback and passing the lint.

Written by the indexing model from the issue text.