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.

plans/ocaml-on-sx.md

@@ -372,6 +372,13 @@ the "mother tongue" closure: OCaml → SX → OCaml. This means:
 
 _Newest first._
 
+- 2026-05-08 Phase 5.1 — baseline expanded to 8 programs (8/8 pass).
+  Added: closures.ml (curried adders), quicksort.ml (recursive sort
+  on lists), exception_handle.ml (exception decl + raise + try/with).
+  All 8 programs together exercise let-rec, modules, refs, for-loops,
+  pattern matching, exceptions, lambdas, list functions, arithmetic.
+  Run.sh streamlined to one sx_server invocation per program (was
+  two). End-to-end runtime ≈2 min for the suite.
 - 2026-05-08 Phase 5.1 — `lib/ocaml/baseline/` with five sample OCaml
   programs (.ml files), driven by `lib/ocaml/baseline/run.sh` through
   `ocaml-run-program (file-read F)`. All 5/5 pass: factorial,