feat: refactor AlgorithmicEvaluator to stateless, add game engine module and holdem_sim CLI

- Refactor AlgorithmicEvaluator from stateful Arc<Evaluator> wrapper to
  pure stateless evaluator with zero-allocation construction
- Extract shared evaluation logic into pub(crate) methods, eliminating
  ~220 lines of duplicated code from Evaluator
- Add game module: table, hand runner, tournament, bots, config, stats
- Add holdem_sim CLI binary crate for running simulations
- Convert MathEvaluator to thread-safe singleton with Arc<Inner> pattern
- Replace heap-allocated combination generation with const-generics
  stack-based approach in AlgorithmicEvaluator::evaluate_n_card_hand
- Add thiserror 2 dependency for GameError derive
- Update docs: README, ACHIEVEMENTS, ROADMAP

holdem_core/src/game/mod.rs

@@ -0,0 +1,52 @@
+//! Texas Hold'em simulation engine.
+//!
+//! This module provides the game engine components for running Texas Hold'em poker
+//! simulations, modeled after the Meerkat API from the University of Alberta's
+//! Poker Academy / OpenTestbed project.
+//!
+//! # Module Structure
+//!
+//! - [`types`] — Core shared types: [`PlayerId`], [`ChipCount`], [`SeatIndex`], [`GameError`]
+//! - [`action`] — Player action types and validation
+//! - [`player_info`] — Per-player state visible to all players
+//! - [`game_info`] — Read-only game state snapshot for bots
+//! - [`player`] — Standardized bot interface ([`HoldemPlayer`]) and internal [`Seat`] struct
+//! - [`betting`] — Betting structures and limits
+//! - [`pot`] — Pot management with side pot algorithm
+//! - [`hand_runner`] — Core state machine that executes a single hand
+//! - [`table`] — Table management with seating, button rotation, and hand execution
+//! - [`tournament`] — Tournament formats, blind schedules, and prize structures
+//! - [`config`] — TOML-based configuration system for game simulations
+
+pub mod action;
+pub mod betting;
+pub mod bot_factory;
+pub mod bots;
+pub mod config;
+pub mod game_info;
+pub mod hand_runner;
+pub mod player;
+pub mod player_info;
+pub mod pot;
+pub mod simulation;
+pub mod stats;
+pub mod table;
+pub mod tournament;
+pub mod types;
+
+// Re-export core types for convenience.
+pub use action::{Action, PlayerAction};
+pub use betting::BetLimit;
+pub use bot_factory::create_bot;
+pub use bots::{CallBot, FoldBot, RandomBot, RaiseBot};
+pub use config::{BetLimitConfig, BotConfig, GameConfig, OutputConfig, SimulationConfig};
+pub use game_info::GameInfo;
+pub use hand_runner::{HandResult, HandRunner, HandState};
+pub use player::{HoldemPlayer, Seat};
+pub use player_info::{PlayerInfo, PlayerState};
+pub use pot::{Pot, PotManager, PotWinner};
+pub use simulation::run_cash_game;
+pub use stats::{PlayerStats, SimulationStats};
+pub use table::{Table, TableConfig};
+pub use tournament::{BlindLevel, BlindSchedule, GameType, PrizeStructure, Tournament};
+pub use types::{ChipCount, GameError, PlayerId, SeatIndex, MAX_SEATS, MIN_PLAYERS};