Set up global store (Zustand)

[lornakelly]

Summary

Introduce a centralized Zustand store for the editor and wire it into the Diagram Editor component so it can consume, modify, and observe application state in a structured and extensible way.

Goals

• Establish a single source of truth for editor state.
• Define a clean state shape for MVP.

Non-Goals

• Full state architecture finalization.
• Advanced middleware (undo/redo, devtools, etc. — can come later).
• Complex performance optimization.

Description

1️⃣ Create Editor Store

• Add a Zustand-based store under src/store/
• The store should define initial state.

2️⃣ Provide Store via Context

• Expose the store via a Provider (if required by chosen architecture).
• Ensure the DiagramEditor component can:
  • Read state from the store
  • Trigger state updates
  • Subscribe to changes

Testing

• Add at least one unit test for:
  • Store initialization
  • A basic action updating state