Improve error management

Error management needs to be improved overall. We need to handle errors/exceptions and give the user meaningful feedback so they can better understand what went wrong.

(This issue should be split into several if racks up to many changes)

No files, tests, entry points, or specific failure cases are identified. First split this broad request into scoped issues with concrete affected areas and acceptance criteria; completion should be defined separately for each error-handling change.

Written by the indexing model from the issue text.