ocaml: phase 5.1 tic_tac_toe.ml baseline (3x3 winner check, X wins top row = 1)

Board as 9-element flat int array, 0=empty, 1=X, 2=O. Three
predicate functions:

  check_row b r       check_col b c       check_diag b

each return the winning player's mark or 0. Main 'winner' loops
i = 0..2 calling row(i)/col(i) then check_diag, threading via a
result ref.

Test board:
  X X X
  . O .
  . . O

X wins on row 0 -> winner returns 1.

Tests Array.of_list with row-major 'b.(r * 3 + c)' indexing,
multi-fn collaboration, and structural equality on int values.

66 baseline programs total.

lib/ocaml/baseline/expected.json

@@ -58,6 +58,7 @@
   "safe_div.ml": 20,
   "shuffle.ml": 55,
   "subset_sum.ml": 8,
+  "tic_tac_toe.ml": 1,
   "word_freq.ml": 8,
   "zip_unzip.ml": 1000,
   "sieve.ml": 15,