Add TypeScript types for types

**Problem**
When working with config, the error messages could be more descriptive.

**Suggestion**
Improve error handling and add detailed error messages.

**Context**
This would help with debugging and maintenance.

Locate the configuration handling entry point and inspect its current error paths, then determine where TypeScript types are defined or needed. Clarify which configuration failures and type declarations are in scope; done should include the requested types and more descriptive error messages, with the relevant existing checks or tests passing.

Written by the indexing model from the issue text.