ocaml: phase 4 Set.Make / Map.Make functor application smoke tests (+3 tests, 572 total)

Functors were already wired through ocaml-make-functor in eval.sx
(curried host closure consuming module dicts) but had no explicit
tests for the user-defined Ord application path. This commit adds
three smoke tests that confirm:

  module IntOrd = struct let compare a b = a - b end
  module S = Set.Make (IntOrd)

  S.elements (fold-add [5;1;3;1;5])    sums to 9 (dedupe + sort)
  S.mem 2 (S.add 1 (S.add 2 (S.add 3 S.empty)))   = true
  M.cardinal (M.add 1 'a' (M.add 2 'b' M.empty))  = 2

The Ord parameter is properly threaded through the functor body —
elements are sorted in compare order and dedupe works.

lib/ocaml/test.sh

@@ -1422,6 +1422,14 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 5171)
 (eval "(ocaml-run \"Char.equal \\\"a\\\" \\\"a\\\"\")")
 
+;; ── Set.Make / Map.Make functor application ──────────────────
+(epoch 5180)
+(eval "(ocaml-run-program \"module IntOrd = struct let compare a b = a - b end ;; module S = Set.Make (IntOrd) ;; let s = List.fold_left (fun s x -> S.add x s) S.empty [5;1;3;1;5] ;; List.fold_left (+) 0 (S.elements s)\")")
+(epoch 5181)
+(eval "(ocaml-run-program \"module IntOrd = struct let compare a b = a - b end ;; module S = Set.Make (IntOrd) ;; let s = S.add 1 (S.add 2 (S.add 3 S.empty)) ;; S.mem 2 s\")")
+(epoch 5182)
+(eval "(ocaml-run-program \"module IntOrd = struct let compare a b = a - b end ;; module M = Map.Make (IntOrd) ;; let m = M.add 1 \\\"a\\\" (M.add 2 \\\"b\\\" M.empty) ;; M.cardinal m\")")
+
 EPOCHS
 
 OUTPUT=$(timeout 360 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
@@ -2261,6 +2269,11 @@ check 5164 "chop_extension hello.ml"      '"hello"'
 check 5170 "Char.compare b a"             '1'
 check 5171 "Char.equal a a"               'true'
 
+# ── Set.Make / Map.Make functor application ─────────────────────
+check 5180 "Set.Make dedupe sum"          '9'
+check 5181 "Set.Make mem"                 'true'
+check 5182 "Map.Make cardinal"            '2'
+
 TOTAL=$((PASS + FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "ok $PASS/$TOTAL OCaml-on-SX tests passed"

plans/ocaml-on-sx.md

@@ -407,6 +407,13 @@ _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.
+- 2026-05-09 Phase 4 — Set.Make / Map.Make functor application
+  smoke tests (+3 tests, 572 total). Functors were already wired
+  through ocaml-make-functor in eval.sx but had no explicit tests
+  for the user-defined Ord application path. Confirms that
+  `module S = Set.Make (IntOrd) ;; let s = ... in S.elements s`,
+  `S.mem 2 s`, and `Map.Make (IntOrd) ;; M.cardinal m` all work end
+  to end.
 - 2026-05-09 Phase 6 — Filename module + Char.compare/equal/escaped
   (+7 tests, 569 total). Filename: basename, dirname, extension,
   chop_extension, concat, is_relative + dir_sep / current_dir_name /