ocaml: phase 5.1 reverse_int.ml baseline (digit-reverse sum = 54329)

Walks digits via mod 10 / div 10, accumulating the reversed value:

  let reverse_int n =
    let m = ref n in
    let r = ref 0 in
    while !m > 0 do
      r := !r * 10 + !m mod 10;
      m := !m / 10
    done;
    !r

  reverse 12345 + reverse 100 + reverse 7
  = 54321 + 1 + 7
  = 54329

Trailing zeros collapse (reverse 100 = 1, not 001).

132 baseline programs total.

plans/ocaml-on-sx.md

@@ -407,6 +407,11 @@ _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.
+- 2026-05-10 Phase 5.1 — reverse_int.ml baseline (digit-reverse,
+  reverse(12345) + reverse(100) + reverse(7) = 54321 + 1 + 7 =
+  54329). Walks digits via mod 10 / div 10, accumulating the
+  reversed value. Trailing zeros collapse (reverse 100 = 1).
+  132 baseline programs total.
 - 2026-05-10 Phase 5.1 — bowling.ml baseline (10-pin bowling score
   for canonical "167" PBA-style game). Walks pin-knockdown list
   applying strike/spare bonuses through a 10-frame counter. Strike