ocaml: phase 5.1 baseline OCaml programs (5/5 pass) + lookahead boundary

lib/ocaml/baseline/{factorial,list_ops,option_match,module_use,sum_squares}.ml
exercised through ocaml-run-program (file-read F). lib/ocaml/baseline/
run.sh runs them and compares against expected.json — all 5 pass.

To make module_use.ml (with nested let-in) parse, parser's
skip-let-rhs-boundary! now uses has-matching-in? lookahead: a let at
depth 0 in a let-decl rhs opens a nested block IFF a matching in
exists before any decl-keyword. Without that in, the let is a new
top-level decl (preserves test 274 'let x = 1 let y = 2').

This is the first piece of Phase 5.1 'vendor a slice of OCaml
testsuite' — handcrafted fixtures for now, real testsuite TBD.

lib/ocaml/baseline/run.sh

@@ -0,0 +1,75 @@
+#!/usr/bin/env bash
+# lib/ocaml/baseline/run.sh — run each baseline OCaml program through
+# ocaml-run-program and compare to expected.json.
+
+set -uo pipefail
+cd "$(git rev-parse --show-toplevel)"
+
+SX_SERVER="${SX_SERVER:-hosts/ocaml/_build/default/bin/sx_server.exe}"
+if [ ! -x "$SX_SERVER" ]; then
+  SX_SERVER="/root/rose-ash/hosts/ocaml/_build/default/bin/sx_server.exe"
+fi
+
+PASS=0
+FAIL=0
+ERRORS=""
+
+for f in lib/ocaml/baseline/*.ml; do
+  name=$(basename "$f")
+  expected=$(grep -oE "\"$name\"[[:space:]]*:[[:space:]]*[0-9-]+" lib/ocaml/baseline/expected.json | sed -E 's/.*:[[:space:]]*//')
+  if [ -z "$expected" ]; then
+    continue
+  fi
+
+  TMP=$(mktemp)
+  cat > "$TMP" << EPOCHS
+(epoch 1)
+(load "lib/guest/lex.sx")
+(load "lib/guest/prefix.sx")
+(load "lib/guest/pratt.sx")
+(load "lib/ocaml/tokenizer.sx")
+(load "lib/ocaml/parser.sx")
+(load "lib/ocaml/eval.sx")
+(load "lib/ocaml/runtime.sx")
+(eval "(ocaml-load-stdlib!)")
+(epoch 2)
+(eval "(ocaml-run-program (file-read \\"$f\\"))")
+EPOCHS
+
+  output=$(timeout 60 "$SX_SERVER" < "$TMP" 2>/dev/null | grep -E '^\(ok-len 2|^\(ok 2' | head -1)
+  rm -f "$TMP"
+
+  # Pull the next line which has the value
+  result=$(timeout 60 "$SX_SERVER" < <(cat <<EPOCHS
+(epoch 1)
+(load "lib/guest/lex.sx")
+(load "lib/guest/prefix.sx")
+(load "lib/guest/pratt.sx")
+(load "lib/ocaml/tokenizer.sx")
+(load "lib/ocaml/parser.sx")
+(load "lib/ocaml/eval.sx")
+(load "lib/ocaml/runtime.sx")
+(eval "(ocaml-load-stdlib!)")
+(epoch 2)
+(eval "(ocaml-run-program (file-read \"$f\"))")
+EPOCHS
+) 2>/dev/null | awk '/^\(ok-len 2 / {getline; print; exit} /^\(ok 2 / {sub(/^\(ok 2 /, ""); sub(/\)$/, ""); print; exit}')
+
+  if [ "$result" = "$expected" ]; then
+    PASS=$((PASS + 1))
+    echo "  ok $name → $result"
+  else
+    FAIL=$((FAIL + 1))
+    ERRORS+="  FAIL $name expected=$expected got=$result
+"
+  fi
+done
+
+TOTAL=$((PASS + FAIL))
+if [ $FAIL -eq 0 ]; then
+  echo "ok $PASS/$TOTAL baseline OCaml programs run correctly"
+else
+  echo "FAIL $PASS/$TOTAL baseline programs"
+  echo "$ERRORS"
+fi
+[ $FAIL -eq 0 ]