Step 5 piece 6: migrate 23 .sx files to define-library/import

Wraps all core .sx files in R7RS define-library with explicit export
lists, plus (import ...) at end for backward-compatible global re-export.

Libraries registered:
  (sx bytecode)      — 83 opcode constants
  (sx render)        — 15 tag registries + render helpers
  (sx signals)       — 23 reactive signal primitives
  (sx r7rs)          — 21 R7RS aliases
  (sx compiler)      — 42 compiler functions
  (sx vm)            — 32 VM functions
  (sx freeze)        — 9 freeze/thaw functions
  (sx content)       — 6 content store functions
  (sx callcc)        — 1 call/cc wrapper
  (sx highlight)     — 13 syntax highlighting functions
  (sx stdlib)        — 47 stdlib functions
  (sx swap)          — 13 swap algebra functions
  (sx render-trace)  — 8 render trace functions
  (sx harness)       — 21 test harness functions
  (sx canonical)     — 12 canonical serialization functions
  (web adapter-html) — 13 HTML renderer functions
  (web adapter-sx)   — 13 SX wire format functions
  (web engine)       — 33 hypermedia engine functions
  (web request-handler) — 4 request handling functions
  (web page-helpers) — 12 page helper functions
  (web router)       — 36 routing functions
  (web deps)         — 19 dependency analysis functions
  (web orchestration) — 59 page orchestration functions

Key changes:
- define-library now inherits parent env (env-extend env instead of
  env-extend make-env) so library bodies can access platform primitives
- sx_server.ml: added resolve_library_path + load_library_file for
  import resolution (maps library specs to file paths)
- cek_run_with_io: handles "import" locally instead of sending to
  Python bridge

2608/2608 tests passing.

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

hosts/ocaml/bin/sx_server.ml

@@ -280,10 +280,44 @@ let flush_batched_io result_str =
     !final
   end
 
+(** Resolve a library spec to a file path.
+    (sx render) → spec/render.sx, (sx bytecode) → lib/bytecode.sx, etc.
+    Returns Some path or None if unknown. *)
+let _lib_base = ref "lib"
+let _spec_base = ref "spec"
+let _web_base = ref "web"
+
+let resolve_library_path lib_spec =
+  let parts = match lib_spec with List l | ListRef { contents = l } -> l | _ -> [] in
+  match List.map (fun v -> match v with Symbol s -> s | String s -> s | _ -> "") parts with
+  | ["sx"; name] ->
+    (* Check spec/ first, then lib/ *)
+    let spec_path = Filename.concat !_spec_base (name ^ ".sx") in
+    let lib_path = Filename.concat !_lib_base (name ^ ".sx") in
+    if Sys.file_exists spec_path then Some spec_path
+    else if Sys.file_exists lib_path then Some lib_path
+    else None
+  | ["web"; name] ->
+    let path = Filename.concat !_web_base (name ^ ".sx") in
+    if Sys.file_exists path then Some path else None
+  | [prefix; name] ->
+    (* Generic: try prefix/name.sx *)
+    let path = Filename.concat prefix (name ^ ".sx") in
+    if Sys.file_exists path then Some path else None
+  | _ -> None
+
+(** Load a library file — parse and evaluate all expressions in the global env.
+    The file should contain a define-library form that registers itself. *)
+let _import_env : env option ref = ref None
+
+let load_library_file path =
+  let env = match !_import_env with Some e -> e | None -> Sx_types.make_env () in
+  let exprs = Sx_parser.parse_file path in
+  List.iter (fun expr -> ignore (Sx_ref.eval_expr expr (Env env))) exprs
+
 (** IO-aware CEK run — handles suspension by dispatching IO requests.
-    When the CEK machine suspends with a perform, this function sends
-    the IO request to the Python bridge, resumes with the response,
-    and repeats until evaluation completes. *)
+    Import requests are handled locally (load .sx file).
+    Other IO requests are sent to the Python bridge. *)
 let cek_run_with_io state =
   let s = ref state in
   let is_terminal s = match Sx_ref.cek_terminal_p s with Bool true -> true | _ -> false in
@@ -295,16 +329,27 @@ let cek_run_with_io state =
     if is_suspended !s then begin
       let request = Sx_runtime.get_val !s (String "request") in
       let op = match Sx_runtime.get_val request (String "op") with String s -> s | _ -> "" in
-      (* Extract args based on operation type *)
-      let args = match op with
+      let response = match op with
         | "import" ->
-          let lib = Sx_runtime.get_val request (String "library") in
-          [String "import"; lib]
+          (* Resolve library locally — load the .sx file *)
+          let lib_spec = Sx_runtime.get_val request (String "library") in
+          let key = Sx_ref.library_name_key lib_spec in
+          if Sx_types.sx_truthy (Sx_ref.library_loaded_p key) then
+            (* Already loaded — just resume *)
+            Nil
+          else begin
+            (match resolve_library_path lib_spec with
+             | Some path -> load_library_file path
+             | None ->
+               Printf.eprintf "[import] WARNING: no file for library %s\n%!"
+                 (Sx_runtime.value_to_str lib_spec));
+            Nil
+          end
         | _ ->
-          let a = Sx_runtime.get_val request (String "args") in
-          (match a with List l -> l | _ -> [a])
+          let args = let a = Sx_runtime.get_val request (String "args") in
+            (match a with List l -> l | _ -> [a]) in
+          io_request op args
       in
-      let response = io_request op args in
       s := Sx_ref.cek_resume !s response;
       loop ()
     end else

hosts/ocaml/lib/sx_ref.ml

@@ -503,7 +503,7 @@ and step_eval_list expr env kont =
 
 (* step-sf-define-library *)
 and step_sf_define_library args env kont =
-  (let lib_spec = (first (args)) in let decls = (rest (args)) in (let lib_env = (env_extend ((make_env ()))) in let exports = ref ((List [])) in let body_forms = ref ((List [])) in (let () = ignore ((List.iter (fun decl -> ignore ((if sx_truthy ((let _and = (list_p (decl)) in if not (sx_truthy _and) then _and else (let _and = (Bool (not (sx_truthy ((empty_p (decl)))))) in if not (sx_truthy _and) then _and else (symbol_p ((first (decl))))))) then (let kind = (symbol_name ((first (decl)))) in (if sx_truthy ((prim_call "=" [kind; (String "export")])) then (exports := (prim_call "append" [!exports; (List (List.map (fun s -> (if sx_truthy ((symbol_p (s))) then (symbol_name (s)) else (String (sx_str [s])))) (sx_to_list (rest (decl)))))]); Nil) else (if sx_truthy ((prim_call "=" [kind; (String "begin")])) then (body_forms := (prim_call "append" [!body_forms; (rest (decl))]); Nil) else Nil))) else Nil))) (sx_to_list decls); Nil)) in (let () = ignore ((List.iter (fun form -> ignore ((eval_expr (form) (lib_env)))) (sx_to_list !body_forms); Nil)) in (let export_dict = (Dict (Hashtbl.create 0)) in (let () = ignore ((List.iter (fun name -> ignore ((if sx_truthy ((env_has (lib_env) (name))) then (sx_dict_set_b export_dict name (env_get (lib_env) (name))) else Nil))) (sx_to_list !exports); Nil)) in (let () = ignore ((register_library (lib_spec) (export_dict))) in (make_cek_value (Nil) (env) (kont)))))))))
+  (let lib_spec = (first (args)) in let decls = (rest (args)) in (let lib_env = (env_extend (env)) in let exports = ref ((List [])) in let body_forms = ref ((List [])) in (let () = ignore ((List.iter (fun decl -> ignore ((if sx_truthy ((let _and = (list_p (decl)) in if not (sx_truthy _and) then _and else (let _and = (Bool (not (sx_truthy ((empty_p (decl)))))) in if not (sx_truthy _and) then _and else (symbol_p ((first (decl))))))) then (let kind = (symbol_name ((first (decl)))) in (if sx_truthy ((prim_call "=" [kind; (String "export")])) then (exports := (prim_call "append" [!exports; (List (List.map (fun s -> (if sx_truthy ((symbol_p (s))) then (symbol_name (s)) else (String (sx_str [s])))) (sx_to_list (rest (decl)))))]); Nil) else (if sx_truthy ((prim_call "=" [kind; (String "begin")])) then (body_forms := (prim_call "append" [!body_forms; (rest (decl))]); Nil) else Nil))) else Nil))) (sx_to_list decls); Nil)) in (let () = ignore ((List.iter (fun form -> ignore ((eval_expr (form) (lib_env)))) (sx_to_list !body_forms); Nil)) in (let export_dict = (Dict (Hashtbl.create 0)) in (let () = ignore ((List.iter (fun name -> ignore ((if sx_truthy ((env_has (lib_env) (name))) then (sx_dict_set_b export_dict name (env_get (lib_env) (name))) else Nil))) (sx_to_list !exports); Nil)) in (let () = ignore ((register_library (lib_spec) (export_dict))) in (make_cek_value (Nil) (env) (kont)))))))))
 
 (* bind-import-set *)
 and bind_import_set import_set env =