Add TypeScript types for store

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

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

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

Start by clarifying whether the requested work is TypeScript types for the store or more descriptive service errors; the title and body describe different changes. No files, tests, or entry points are named, so identify the relevant store and service code before defining the expected types or error messages. Done should include an agreed scope and tests or examples showing the intended behavior.

Written by the indexing model from the issue text.