Tasks: Blackjack Split

Phase 1: Core State Refactor

Purpose: Replace the single player hand model with a split-ready round structure.

T001 Refactor src/games/blackjack/gameLogic.ts to use playerHands: Card[][] and activeHandIndex in the round state.
T002 Update tests/unit/blackjackLogic.test.ts to assert the new split-ready state shape while preserving the existing blackjack behavior.
T003 Keep the existing UI compiling by maintaining any temporary compatibility needed during the state transition.

Purpose: Add split gating before any hand-duplication logic is exposed to the UI.

T004 Implement split eligibility checks for initial two-card matching values.
T005 Validate the additional split wager against the shared wallet before applying the split.
T006 Add unit tests for invalid split attempts, including insufficient funds and ineligible hands.

Purpose: Resolve split hands one at a time and preserve the new active hand state.

T007 Implement sequential hand progression with activeHandIndex advancing only after the current hand finishes.
T008 Add support for per-hand resolution outcomes and aggregate round settlement.
T009 Add unit tests for sequential resolution across two split hands.

Purpose: Enforce the stricter rules for split Aces.

T010 Implement the one-card-only rule for split Aces and auto-end the turn after the card is dealt.
T011 Treat split Ace + 10-value hands as 1:1 wins instead of natural blackjack payouts.
T012 Add unit tests for split Ace auto-end behavior and payout handling.

Purpose: Expose split hands visually once the state model is stable.

T013 Update the Blackjack UI to render multiple hands and highlight the active one.
T014 Add UI regression tests for multi-hand rendering and active-hand indicators.