Restore cek_run IO hooks and cek_step_loop error handling lost by bootstrap

bootstrap.py regenerated cek_run as a simple "raise if suspended" without
the _cek_io_resolver and _cek_io_suspend_hook checks. Also lost the
CekPerformRequest catch in cek_step_loop and step_limit checks.

This was the direct cause of "IO suspension in non-IO context" when island
click handlers called perform (via hs-wait). The CEK had no way to propagate
the suspension to the VM/JS boundary.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

hosts/ocaml/lib/sx_ref.ml

@@ -576,11 +576,34 @@ and expand_macro mac raw_args env =
 
 (* cek-step-loop *)
 and cek_step_loop state =
-  (if sx_truthy ((let _or = (cek_terminal_p (state)) in if sx_truthy _or then _or else (cek_suspended_p (state)))) then state else (cek_step_loop ((cek_step (state)))))
+  if !step_limit > 0 then begin
+    step_count := !step_count + 1;
+    if !step_count > !step_limit then
+      raise (Sx_types.Eval_error "TIMEOUT: step limit exceeded")
+  end;
+  (if sx_truthy ((let _or = (cek_terminal_p (state)) in if sx_truthy _or then _or else (cek_suspended_p (state)))) then state else begin
+    let next = (try cek_step (state)
+      with Sx_types.CekPerformRequest request ->
+        make_cek_suspended request (cek_env state) (cek_kont state))
+    in cek_step_loop next
+  end)
 
-(* cek-run *)
+(* cek-run — with IO suspension hooks for the OCaml host *)
 and cek_run state =
-  (let final = (cek_step_loop (state)) in (if sx_truthy ((cek_suspended_p (final))) then (raise (Eval_error (value_to_str (String "IO suspension in non-IO context")))) else (cek_value (final))))
+  let rec run s =
+    let final = cek_step_loop s in
+    if sx_truthy (cek_suspended_p final) then
+      match !Sx_types._cek_io_resolver with
+      | Some resolver ->
+        let request = cek_io_request final in
+        let result = resolver request final in
+        run (cek_resume final result)
+      | None ->
+        (match !Sx_types._cek_io_suspend_hook with
+         | Some hook -> hook final
+         | None -> raise (Eval_error (value_to_str (String "IO suspension in non-IO context"))))
+    else cek_value final
+  in run state
 
 (* cek-resume *)
 and cek_resume suspended_state result' =