ocaml: phase 6 Array module + (op) operator sections (+6 tests, 512 total)

Array module (runtime.sx, OCaml syntax):
  Backed by a 'ref of list'. make/length/get/init build the cell;
  set rewrites the underlying list with one cell changed (O(n) but
  works for short arrays in baseline programs). Includes
  iter/iteri/map/mapi/fold_left/to_list/of_list/copy/blit/fill.

(op) operator sections (parser.sx, parse-atom):
  When the token after '(' is a binop (any op with non-zero
  precedence in the binop table) and the next token is ')', emit
  (:fun ('a' 'b') (:op OP a b)) — i.e. (+)  becomes fun a b -> a + b.
  Recognises every binop including 'mod', 'land', '^', '@', '::',
  etc.

Lets us write:
  List.fold_left (+) 0 [1;2;3;4;5]    = 15
  let f = ( * ) in f 6 7              = 42
  List.map ((-) 10) [1;2;3]           = [9;8;7]
  let a = Array.make 5 7 in
  Array.set a 2 99;
  Array.fold_left (+) 0 a             = 127

lib/ocaml/test.sh

@@ -1262,6 +1262,22 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 5002)
 (eval "(ocaml-run \"List.map (fun x -> match x with `On -> 1 | `Off -> 0) [`On; `Off; `On]\")")
 
+;; ── Array module ─────────────────────────────────────────────
+(epoch 5010)
+(eval "(ocaml-run \"let a = Array.make 5 7 in Array.set a 2 99; Array.fold_left (+) 0 a\")")
+(epoch 5011)
+(eval "(ocaml-run \"let a = Array.init 4 (fun i -> i * i) in Array.fold_left (+) 0 a\")")
+(epoch 5012)
+(eval "(ocaml-run \"let a = Array.make 3 0 in for i = 0 to 2 do Array.set a i (i + 1) done; Array.length a + Array.get a 0 + Array.get a 1 + Array.get a 2\")")
+
+;; ── (op) operator sections ───────────────────────────────────
+(epoch 5020)
+(eval "(ocaml-run \"List.fold_left (+) 0 [1;2;3;4;5]\")")
+(epoch 5021)
+(eval "(ocaml-run \"let f = ( * ) in f 6 7\")")
+(epoch 5022)
+(eval "(ocaml-run \"List.map ((-) 10) [1;2;3]\")")
+
 EPOCHS
 
 OUTPUT=$(timeout 360 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
@@ -2004,6 +2020,16 @@ check 5000 'match polyvar Foo / Bar'      '1'
 check 5001 'match polyvar Pair (a, b)'    '12'
 check 5002 'List.map polyvar On / Off'    '(1 0 1)'
 
+# ── Array module ────────────────────────────────────────────────
+check 5010 "Array.make + set 2 99"        '127'
+check 5011 "Array.init 4 i*i"             '14'
+check 5012 "Array.make 3 + for + length"  '9'
+
+# ── (op) operator sections ──────────────────────────────────────
+check 5020 "fold_left (+) sum"            '15'
+check 5021 "let f = (*) in f 6 7"         '42'
+check 5022 "List.map ((-) 10) [1;2;3]"    '(9 8 7)'
+
 TOTAL=$((PASS + FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "ok $PASS/$TOTAL OCaml-on-SX tests passed"