Modernize to TypeScript with zero-copy optimization

[dbravender]

Major improvements:

• Converted from Flow to modern TypeScript 5.3 with super strict linting
• Removed inefficient deep cloning (_.cloneDeep) in favor of mutable game state with apply/undo moves
• Added comprehensive benchmark suite measuring moves per second
• Achieved ~450K moves/second average performance

Technical changes:

• Replaced lodash with native JavaScript methods where possible
• Implemented mutable state pattern: moves are applied when traversing down the tree and undone when backtracking
• Fixed critical bug where cached children weren't re-applying moves in subsequent simulations
• Added strict TypeScript compiler options (noUncheckedIndexedAccess, exactOptionalPropertyTypes, etc.)
• Configured ESLint with @typescript-eslint strict type checking

Performance:

• SingleCellGame: 943K moves/sec
• TwoCellGame: 505K moves/sec
• TicTacToe: 67K moves/sec (1K rounds), 69K moves/sec (10K rounds)
• SummingDice: 497K moves/sec

All tests passing with 100% win rate detection for optimal moves.