Update store documentation

**Problem**
When working with core, 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 does not name a file, test, or entry point. Start by locating the core store implementation and its existing error handling, then clarify which errors and documentation need changes. Done means the requested error messages are more descriptive and the store documentation is updated, with relevant checks passing.

Written by the indexing model from the issue text.