ocaml: phase 5.1 anagrams.ml baseline (18/18 pass)

Group anagrams by canonical (sorted-chars) key using Hashtbl +
List.sort. Demonstrates char-by-char traversal via String.get + for-loop +
ref accumulator + Hashtbl as a multi-valued counter.

lib/ocaml/baseline/anagrams.ml

@@ -0,0 +1,26 @@
+(* Baseline: count anagram groups using Hashtbl + sort *)
+
+(* Sort the chars in a string to get its anagram-equivalence key *)
+let canonical s =
+  let n = String.length s in
+  let chars = ref [] in
+  for i = 0 to n - 1 do
+    chars := (String.get s i) :: !chars
+  done ;
+  let sorted = List.sort compare !chars in
+  String.concat "" sorted
+;;
+
+let count_groups words =
+  let counts = Hashtbl.create 16 in
+  List.iter
+    (fun w ->
+      let k = canonical w in
+      match Hashtbl.find_opt counts k with
+      | None -> Hashtbl.add counts k 1
+      | Some n -> Hashtbl.replace counts k (n + 1))
+    words ;
+  Hashtbl.length counts
+;;
+
+count_groups ["eat"; "tea"; "tan"; "ate"; "nat"; "bat"]

lib/ocaml/baseline/expected.json

@@ -1,4 +1,5 @@
 {
+  "anagrams.ml": 3,
   "btree.ml": 39,
   "calc.ml": 13,
   "closures.ml": 315,

plans/ocaml-on-sx.md

@@ -407,6 +407,9 @@ _Newest first._
   binary search tree (`type 'a tree = Leaf | Node of 'a * 'a tree *
   'a tree`) with insert + in-order traversal. Tests parametric ADT,
   recursive match, List.append, List.fold_left.
+- 2026-05-08 Phase 5.1 — anagrams.ml baseline (18/18 pass). Counts
+  anagram-equivalence groups via Hashtbl + List.sort + String.get +
+  for-loop. `["eat";"tea";"tan";"ate";"nat";"bat"]` → 3 groups.
 - 2026-05-08 Phase 5.1 — lambda_calc.ml baseline (17/17 pass). Untyped
   lambda calculus interpreter using two ADTs (`type term = Var | Abs |
   App | Num`, `type value = VNum | VClos`), an env as `(string * value)