Implement visible graph rendering for users. #26
Description
Enable users to see the current state of the graph through a visual representation. This issue focuses on exposing the graph's structure in a way that a UI layer can render it, without mixing UI logic into the core features of the calculator.
The goal is to provide a clean surface that any frontend can use to draw the graph.
- Provide a structured, UI-friendly representation of the graph.
- Allow the UI to retrieve node positions, types, and connections.
- Ensure updates to the graph (create/move/delete/connect) can be reflected visually.
- Keep rendering logic outside the engine; expose data only