Restart game feature

Save initial game state with #80

Consider:
* provide a way in the UI to restart the game without reloading the page AND/OR
* could simply be an interaction command, and a button (furniture) in the final screen (room) which would restore the initial game state

Review the initial game-state work tracked in #80 and trace the game-state, UI, interaction-command, and final-screen room entry points mentioned here. Clarify whether restart should be a UI control, an interaction command, or both; done means restoring the saved initial state without reloading and covering the chosen trigger or triggers.

Written by the indexing model from the issue text.