Add TypeScript types for store

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

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

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

The issue names the store and controllers but no files, tests, or entry points. Start by locating those areas and checking how errors are currently handled; done means TypeScript types are added for the store and controller errors provide more detailed messages.

Written by the indexing model from the issue text.