feat: implement complete score tracking system

- Track score (starts at 0)
- +1 score and +1 correct for each correct character typed
- -1 score and +1 missed for each wrong character typed
- +1 deaths for each collision with ship
- Score resets when game starts
- All metrics exposed through ScoreManager
- Updated example app UI with colorful scoreboard showing:
  - Time (gray)
  - Score (neutral)
  - Correct (green)
  - Missed (yellow)
  - Deaths (red)
  - Keystrokes (neutral)
- Uses grid layout for organized metric display
- Score cannot go below 0 (clamped to minimum)

src/types.ts

@@ -82,6 +82,10 @@ export type CursorManager = {
 export type ScoreManager = {
   timeValue: number;
   totalKeystrokes: number;
+  score: number;
+  correct: number;
+  missed: number;
+  deaths: number;
 };
 
 // ============================================================================
@@ -94,13 +98,18 @@ export type GameStatusManager = {
   startGame: () => void;
   quitGame: () => void;
   level: number;
-  score: number;
-  togglePause: () => void;
   shipState: ShipState;
   shipExplosionTime: number;
   updatePlayerX: (x: number) => void;
   handleTypedLetter: (letter: string) => void;
   setGameLoopCallback: (callback: (deltaTime: number, letters: FallingLetter[]) => void) => void;
+  addCorrect: () => void;
+  addMissed: () => void;
+  addDeath: () => void;
+  score: number;
+  correct: number;
+  missed: number;
+  deaths: number;
 };
 
 // ============================================================================