nx_tictactoe_test.nx

nx_tictactoe_test.nx -- C0 substrate smoke. 12 deterministic assertions covering: 1. new game has X to move + outcome ongoing 2. 9 legal moves on a fresh board 3. apply X to cell 4 -> board[4]=X, turn=O, 8 legal moves left 4. illegal-move (occupied cell) is no-op 5. illegal-move (out-of-range) is no-op 6. horizontal-row win is detected (top row XXX) 7. diagonal win is detected (0-4-8 XXX) 8. draw is detected after 9 non-winning moves 9. state-hash is deterministic for same state 10. perfect-vs-perfect always ends in draw (game-theory invariant) 11. perfect-vs-random never loses (perfect's score never negative) 12. evaluate updates only the OUTCOME and WINNER cells (does not mutate board) Each failed assertion exits with a distinct non-zero code so the smoke harness identifies which check fired. Composes [[feedback-bug-class-prevention-additive-not-restrictive]] + §22 bug-class table entry "move-applies-to-wrong-cell" (the tic-tac-toe equivalent of the W/S inversion class).