The pause indicator was showing 'paused' while the game was still running
because isManualPaused was being modified by both user actions (clicking
pause button) and system actions (opening menu).
Changes:
- systemStore: pause()/resume() no longer modify isManualPaused, only
togglePause() does (with optimistic update + rollback on failure)
- useGameControl: consolidate 3 overlapping watches into 1 clean watch
that only handles menu open/close without polluting manual pause state
- App.vue: explicitly call resumeGame() API when game initializes
Add splash layer, support game start, settings, exit
Modify settings layer, add "go back to splash" and "exit"
Add character threshold for history input
Closes#28
