feat: prepare vim-sudoku for unified API implementation

- Archive previous implementation attempt (src -> src_failed)
- Create comprehensive IMPLEMENTATION_PLAN.md with phased approach
- Create IMPLEMENTATION.md to track implementation progress
- Update example app to match vim-maze patterns:
  - Simplify UI to desktop-only (no mobile support)
  - Add score metrics display (time, keystrokes, final score)
  - Update instructions for sudoku-specific keys (hjkl, i for edit)
  - Remove unnecessary mobile hooks

Phase 5 complete. Ready to begin Phase 10 (Setup & Core Types).

src/types.ts

@@ -1,35 +0,0 @@
-import type { RefObject } from 'react';
-
-export type { Coord, SudokuBoard, SudokuCell, Difficulty } from './useBoard/types';
-export type { CursorManager, CursorMode, GameKeyManager, KeyLogEntry } from './useCursor/types';
-export type { GameStatus, GameStatusManager } from './useGameStatus/types';
-export type { ScoreManager, TimerManager } from './useScore/types';
-
-export type GameOptions = {
-  difficulty?: Difficulty;
-};
-
-export type GameManager = {
-  containerRef: RefObject<HTMLDivElement | null>;
-  renderBoard: () => void;
-  gameStatus: GameStatus;
-  setGameStatus: (status: GameStatus) => void;
-  startGame: () => void;
-  togglePause: (pause?: boolean) => void;
-  quitGame: () => void;
-  cursor: CursorManager;
-  scoreManager: ScoreManager;
-  keyLog: KeyLogEntry[];
-  clearKeyLog: () => void;
-  getKeyLog: () => KeyLogEntry[];
-  board: {
-    generateBoard: (difficulty: Difficulty) => void;
-    solveBoard: () => boolean;
-    resetBoard: () => void;
-    getCell: (row: number, col: number) => any;
-    setCell: (row: number, col: number, value: string) => boolean;
-    canEditCell: (row: number, col: number) => boolean;
-    isComplete: () => boolean;
-    isFullyValid: () => boolean;
-  };
-};