ocaml: wire dynamic-wind through CEK — WindFrame + winders stack

- sx_types.ml: CallccContinuation gains winders depth int field
- sx_runtime.ml: make_callcc_continuation(captured, winders_len),
  callcc_continuation_winders_len accessor; get_val maps after-thunk,
  winders-len, body-result to cf_f/cf_extra/cf_name
- sx_ref.ml: step_limit/step_count restored; make_wind_after_frame and
  make_wind_return_frame now store their args in the CekFrame fields
- transpiler.sx: after-thunk→cf_f, winders-len→cf_extra,
  body-result→cf_name for future bootstrap runs
- 8 new dynamic-wind tests pass (OCaml), 235/235 no regressions

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

hosts/ocaml/transpiler.sx

@@ -256,6 +256,7 @@
     "callcc-continuation?"
     "callcc-continuation-data"
     "make-callcc-continuation"
+    "callcc-continuation-winders-len"
     "dynamic-wind-call"
     "strip-prefix"
     "component-set-param-types!"
@@ -295,7 +296,8 @@
     "*bind-tracking*"
     "*provide-batch-depth*"
     "*provide-batch-queue*"
-    "*provide-subscribers*"))
+    "*provide-subscribers*"
+    "*winders*"))
 
 (define
   ml-is-mutable-global?
@@ -533,13 +535,13 @@
               "; cf_env = "
               (ef "env")
               "; cf_name = "
-              (if (= frame-type "if") (ef "else") (ef "name"))
+              (if (= frame-type "if") (ef "else") (cond (some (fn (k) (= k "body-result")) items) (ef "body-result") :else (ef "name")))
               "; cf_body = "
               (if (= frame-type "if") (ef "then") (ef "body"))
               "; cf_remaining = "
               (ef "remaining")
               "; cf_f = "
-              (ef "f")
+              (cond (some (fn (k) (= k "after-thunk")) items) (ef "after-thunk") (some (fn (k) (= k "f")) items) (ef "f") :else "Nil")
               "; cf_args = "
               (cond
                 (some (fn (k) (= k "evaled")) items)
@@ -582,6 +584,8 @@
                 (ef "prev-tracking")
                 (some (fn (k) (= k "extra")) items)
                 (ef "extra")
+                (some (fn (k) (= k "winders-len")) items)
+                (ef "winders-len")
                 :else "Nil")
               "; cf_extra2 = "
               (cond