Step 17b: bytecode-compiled text-layout, WASM library import fix

- text-layout.sx added to WASM bytecode pipeline (9K compiled)
- Fix multi-list map calls (map-indexed + nth instead of map fn list1 list2)
- pretext-layout-lines and pretext-position-line moved to library exports
- Browser load-sxbc: handle VmSuspended for import, copy library exports
  to global_env after module load (define-library export fix)
- compile-modules.js: text-layout in SOURCE_MAP, FILES, and entry deps
- Island uses library functions (break-lines, pretext-layout-lines)
  instead of inlining — runs on bytecode VM when exports resolve

Known issue: define-library exports don't propagate to browser global env
yet. The load-sxbc import suspension handler resumes correctly but
bind_import_set doesn't fire. Needs deeper investigation into how the
WASM kernel's define-library registers exports vs how other libraries
(adapter-html, tw) make their exports available.

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

hosts/ocaml/browser/compile-modules.js

@@ -47,6 +47,7 @@ const SOURCE_MAP = {
   'engine.sx': 'web/engine.sx', 'orchestration.sx': 'web/orchestration.sx',
   'boot.sx': 'web/boot.sx',
   'tw-layout.sx': 'web/tw-layout.sx', 'tw-type.sx': 'web/tw-type.sx', 'tw.sx': 'web/tw.sx',
+  'text-layout.sx': 'lib/text-layout.sx',
 };
 let synced = 0;
 for (const [dist, src] of Object.entries(SOURCE_MAP)) {
@@ -79,6 +80,7 @@ const FILES = [
   'page-helpers.sx', 'freeze.sx', 'bytecode.sx', 'compiler.sx', 'vm.sx',
   'dom.sx', 'browser.sx', 'adapter-html.sx', 'adapter-sx.sx', 'adapter-dom.sx',
   'tw-layout.sx', 'tw-type.sx', 'tw.sx',
+  'text-layout.sx',
   'boot-helpers.sx', 'hypersx.sx', 'harness.sx', 'harness-reactive.sx',
   'harness-web.sx', 'engine.sx', 'orchestration.sx',
   // Hyperscript modules — loaded on demand via transparent lazy loader
@@ -478,6 +480,10 @@ if (entryFile) {
   for (const m of HS_LAZY) {
     if (manifest[m] && !lazyDeps.includes(m)) lazyDeps.push(m);
   }
+  // Text layout library — loaded eagerly for Pretext island
+  if (manifest['sx text-layout'] && !eagerDeps.includes('sx text-layout')) {
+    eagerDeps.push('sx text-layout');
+  }
   manifest['_entry'] = {
     file: entryFile.file,
     deps: eagerDeps,

hosts/ocaml/browser/sx_browser.ml

@@ -685,8 +685,45 @@ let () =
       in
       let module_val = convert_code code_form in
       let code = Sx_vm.code_from_value module_val in
-      let _result = Sx_vm.execute_module code _vm_globals in
+      (* 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
+       | _ -> ());
       Number (float_of_int (Hashtbl.length _vm_globals))
     | _ -> raise (Eval_error "load-sxbc: expected (sxbc version hash (code ...))"));