Fix three code bugs

[RueHaile]

Fix game logic, stability, and portability issues by improving card handling, war resolution, and adding a missing include.

The war resolution logic was particularly problematic. Previously, if a player ran out of cards mid-war, the game would print an error and return, leaving game state inconsistent and potentially unresolvable. The fix now ensures that if one player can continue, they win the current pot and remaining cards, and if neither can continue, all piles are cleared for a clean game end. This prevents deadlocks and ensures proper game termination. The NO_CARD sentinel addresses a subtle logic error where 0 (a valid card) was used to indicate no cards, leading to incorrect comparisons and game outcomes during ties or war.

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[cursor]

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
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