Saving state: saving, restoring, restarting, quitting

These four are signals, not implementations: each emits a platform event that the engine processes after the turn through client-registered hooks. The client owns persistence and the confirmation UI. Verbs that parse: save/save game, restore/load/load game/restore game, quit/q/exit game, restart. Named saves are dormant (no slot in the grammar). Quit asks for confirmation through a client query, but with no client hook registered it auto-confirms and stops; restart computes whether confirmation is warranted (unsaved progress, more than a few moves) and leaves honoring it to the hook.

The player sees (in a client that registers no hooks, like the bare test harness, where the signal side is all there is):

> save
Save failed.

> restore
No saved games found.

"Save failed." is the engine reporting an unhandled platform-save-requested; a real client's hook would have completed it. Quit and restart print nothing of their own here for the same reason.