ocaml: phase 5.1 baseline 8/8 — quicksort + exceptions + closures

Added 3 baseline programs:
- closures.ml — curried make_adder; verifies closure capture
- quicksort.ml — recursive sort using List.filter + List.append, sums result
- exception_handle.ml — exception NegArg of int + raise + try/with

All 8/8 baseline programs pass through ocaml-run-program. Combined the
suite exercises: let-rec, modules, refs, for-loops, pattern matching,
exceptions, lambdas, list ops (map/filter/append/fold), arithmetic.

run.sh streamlined to one sx_server invocation per program. End-to-end
runtime ≈2 min.

lib/ocaml/baseline/closures.ml

@@ -0,0 +1,5 @@
+(* Baseline: closures + curried application *)
+let make_adder n = fun x -> n + x ;;
+let add5 = make_adder 5 ;;
+let add10 = make_adder 10 ;;
+add5 100 + add10 200