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/exception_handle.ml

@@ -0,0 +1,17 @@
+(* Baseline: exception declaration + raise + try-with *)
+exception NegArg of int ;;
+let safe_sqrt n =
+  if n < 0 then raise (NegArg n)
+  else
+    begin
+      let rec find_sqrt i =
+        if i * i > n then i - 1
+        else find_sqrt (i + 1)
+      in find_sqrt 0
+    end ;;
+let result =
+  try
+    safe_sqrt 16
+  with
+  | NegArg _ -> 0 ;;
+result