Tic-Tac-Toe: prioritize wins, blocks, and fork control

In Tic-Tac-Toe, check for an immediate win, then an immediate block, before pursuing a fork. The center participates in four lines and corners in three, but the correct move depends on the exact board. Prevent an opponent from creating two threats at once, and use symmetry to reduce duplicate cases. For a rules or result issue, include board dimensions, win length, full position, player to move, and move history.