[TILT-31] [TILT] PBT: GTO calculator — probability sum and strategy bounds

[Jonathangadeaharder]

Migrated from Plane | ID: TILT-31 | Priority: high | State: Backlog

PBT — GTO Calculator
Parent epic: Add Property-Based Testing to Tilt
Target: GTO strategy calculation

Properties:

1. Probabilities sum to 1: All action probabilities (fold, call, raise) sum to 1.0 within epsilon (1e-9)
2. Mixed strategies bounded: For mixed strategies, 0 < p(action) < 1 for all available actions
3. Pure strategy: When optimal, one action has probability 1.0 and others have 0.0
4. No negative probabilities: All probabilities are ≥ 0

Generator Strategy:

• arbGameState() — generates valid game states (stack sizes, pot, position, cards)
• arbRange() — generates hand ranges for opponent modeling

Acceptance Criteria:

• At least 3 property tests
• Probability sum verified with 1000+ game states