fix: center text and ship for sentences mode

- Ensure ship moves to and stays at center (400px) during sentence mode
- Remove width constraint to allow full text centering calculation
- Always call moveTowardTarget to smoothly center the ship
- Remove unused MAX_TEXT_WIDTH constant

src/useGame/useGame.ts

@@ -38,6 +38,7 @@ export function useGame(
     } else {
       // Keep ship centered for sentence/paragraph mode
       cursorManager.setTargetX(400); // Canvas center
+      cursorManager.moveTowardTarget(deltaTime); // Move to center but don't track letters
     }
     
     renderBoardWrapped(letters);