Fix Pretext island: library functions inside define-library begin block

Root cause: sx_insert_near placed break-lines-greedy, pretext-position-line,
pretext-layout-lines OUTSIDE the define-library begin block. The bytecode
compiler only compiles forms inside begin as STORE_GLOBAL — forms outside
are invisible to the browser VM.

Fix: moved all function definitions inside (begin ...) of (define-library).
Bytecode now includes all 17 functions (11K compiled, was 9K).

Browser load-sxbc: simplified VmSuspended handling — just catch and
continue, since STORE_GLOBAL ops already ran before the import OP_PERFORM.
sync_vm_to_env copies them to global_env.

Island now calls break-lines and pretext-layout-lines from bytecode-compiled
library — runs on VM, not CEK interpreter.

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

hosts/ocaml/browser/sx_browser.ml

@@ -688,42 +688,12 @@ let () =
       (* Use execute_module_safe to handle import suspension.
          Libraries compiled from define-library + import emit OP_PERFORM
          at the end; we catch and resolve the import inline. *)
-      let run_module c =
-        let rec handle_result r =
-          match r with
-          | Ok _result -> ()
-          | Error (request, saved_vm) ->
-            (* Import suspension — library body already ran and registered.
-               Copy exports to global env, then resume the VM. *)
-            let lib_spec = Sx_runtime.get_val request (String "library") in
-            (try ignore (Sx_ref.bind_import_set lib_spec (Env global_env))
-             with _ -> ());
-            let next = try Ok (Sx_vm.resume_vm saved_vm Nil)
-              with Sx_vm.VmSuspended (req2, vm2) -> Error (req2, vm2) in
-            handle_result next
-        in
-        handle_result (Sx_vm.execute_module_safe c _vm_globals)
-      in
-      run_module code;
-      sync_vm_to_env ();
-      (* After loading, copy any new library exports to global env.
-         define-library registers exports in _library_registry_;
-         the import OP_PERFORM can't execute bind_import_set in bytecode,
-         so we manually copy exports that aren't yet in global_env. *)
-      (match Sx_ref._library_registry_ with
-       | Dict registry ->
-         Hashtbl.iter (fun _key entry ->
-           (match Sx_runtime.get_val entry (String "exports") with
-            | Dict exports ->
-              Hashtbl.iter (fun name value ->
-                if not (Sx_types.env_has global_env name) then begin
-                  ignore (Sx_types.env_bind global_env name value);
-                  Hashtbl.replace _vm_globals name value
-                end
-              ) exports
-            | _ -> ())
-         ) registry
+      (try
+        ignore (Sx_vm.execute_module code _vm_globals)
+       with
+       | Sx_vm.VmSuspended _ -> ()  (* Import suspension — defines already in globals *)
        | _ -> ());
+      sync_vm_to_env ();
       Number (float_of_int (Hashtbl.length _vm_globals))
     | _ -> raise (Eval_error "load-sxbc: expected (sxbc version hash (code ...))"));