Backend should maintain session id so frontend knows if it should reset its state.

Development use case is when you restart the backend and you need to clear the state manually in the browser.

Trace how the backend and frontend currently store and exchange application state; no files or tests are identified in the issue. Determine how a backend-maintained session identifier should reach the frontend and how the frontend detects a changed session. Done means restarting the backend lets the frontend recognize the new session and reset its state without manual browser clearing.

Written by the indexing model from the issue text.