ocaml: phase 5.1 word_count.ml baseline (10/10 pass)

Uses Map.Make(StrOrd) + List.fold_left to count word frequencies;
exercises the full functor pipeline with a real-world idiom:

  let inc_count m word =
    match StrMap.find_opt word m with
    | None -> StrMap.add word 1 m
    | Some n -> StrMap.add word (n + 1) m
  let count words = List.fold_left inc_count StrMap.empty words

10/10 baseline programs pass.

lib/ocaml/baseline/expected.json

@@ -7,5 +7,6 @@
   "module_use.ml": 3,
   "option_match.ml": 5,
   "quicksort.ml": 44,
-  "sum_squares.ml": 385
+  "sum_squares.ml": 385,
+  "word_count.ml": 3
 }

lib/ocaml/baseline/word_count.ml

@@ -0,0 +1,14 @@
+(* Baseline: word-frequency map over a list using Map.Make + List.fold_left *)
+module StrOrd = struct let compare a b = compare a b end ;;
+module StrMap = Map.Make(StrOrd) ;;
+
+let inc_count m word =
+  match StrMap.find_opt word m with
+  | None -> StrMap.add word 1 m
+  | Some n -> StrMap.add word (n + 1) m
+;;
+
+let count words = List.fold_left inc_count StrMap.empty words ;;
+
+let m = count ["the"; "fox"; "the"; "dog"; "the"; "fox"] ;;
+StrMap.find "the" m