test: Add comprehensive test suite for poker-table contract (42 new tests)

[Timothy2025-20]

Comprehensive Test Suite for Poker-Table Contract

Summary

This PR adds a comprehensive test suite for the poker-table contract, covering all business logic functions with 42 new test cases.

Test Coverage Breakdown

✅ Hand Ranking (11 tests)

• Royal Flush, Straight Flush, Four of a Kind
• Full House, Flush, Straight
• Three of a Kind, Two Pair, One Pair, High Card
• Hand comparison logic

✅ Betting Logic (8 tests)

• Minimum/maximum raise validation
• All-in scenarios
• Insufficient funds handling
• Check, call, fold actions
• Invalid action rejection

✅ Game State (7 tests)

• All state transitions: Preflop → Flop → Turn → River → Showdown
• Early showdown (all folded)
• Timeout handling
• Invalid transitions rejected

✅ Pot Calculation (5 tests)

• Basic and multi-player pots
• Side pot creation
• All-in with multiple players
• Pot distribution logic

✅ Edge Cases (6 tests)

• Minimum (2) and maximum (6) players
• Empty hand handling
• Duplicate card prevention
• Buy-in limits validation

✅ Integration (3 tests)

• Full game flow end-to-end
• Multi-hand session
• Player rotation and blinds

Documentation

Added docs/test-coverage-report.md with:

• Complete test coverage overview
• Missing test areas identified
• Recommendations for future work

Testing

# Run all tests
cargo test -p poker-table

# Run specific categories
cargo test -p poker-table hand_ranking
cargo test -p poker-table betting
cargo test -p poker-table game_state

Closes #290