feat(codegen): export pub fn to WASM (both codegen.ml + codegen_gc.ml)

The AST has carried `fd_vis : visibility` since forever; the parser has
accepted `pub fn` since forever; the `PUB` token has been wired through
lexer + parser_driver. Only the two WASM backends (codegen.ml:1724 and
codegen_gc.ml:1110) were ignoring `fd_vis` and instead consulting a
hardcoded name allowlist:

  ["main"; "init_state"; "step_state"; "get_state"; "mission_active"]

This commit makes both backends honour `fd_vis = Public` as well. The
game-hook allowlist is retained verbatim for backward compat with
pre-`pub` programs (IDApTIK CharacterSelect bridge et al.), so:

  - `pub fn foo() -> Bool`  — exported (new)
  - `fn main() -> ()`        — exported (backward compat)
  - `fn helper() -> Int`     — not exported (unchanged)

Verified via `/tmp/multi_pub_test.affine`: three `pub fn test_*` all
appear in the WASM export list; a non-`pub` helper does not.

Unblocks the `affinescript-deno-test` MVP's one-test-per-file
constraint — the harness can now discover multiple `test_*` exports
per file via `module.functionExports.filter(n => n.startsWith('test_'))`.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

lib/codegen.ml

@@ -1721,9 +1721,13 @@ let gen_decl (ctx : context) (decl : top_level) : context result =
     let* (ctx_after_gen, func) = gen_function ctx_with_func_idx fd in
     let func_with_type = { func with f_type = type_idx } in
 
-    (* Add export for main and control helpers *)
-    let export_names = ["main"; "init_state"; "step_state"; "get_state"; "mission_active"] in
-    let export = if List.mem fd.fd_name.name export_names then
+    (* Export function if marked `pub` OR if its name matches a reserved
+       game-loop hook (preserved for backward compatibility with the
+       IDApTIK CharacterSelect bridge and the pre-`pub` compiler behaviour). *)
+    let game_hook_names = ["main"; "init_state"; "step_state"; "get_state"; "mission_active"] in
+    let is_pub = (fd.fd_vis = Ast.Public) in
+    let is_game_hook = List.mem fd.fd_name.name game_hook_names in
+    let export = if is_pub || is_game_hook then
       [{ e_name = fd.fd_name.name; e_desc = ExportFunc func_idx }]
     else
       []

lib/codegen_gc.ml

@@ -1111,11 +1111,16 @@ let gen_gc_decl (ctx : gc_ctx) (decl : top_level) : gc_ctx cg_result =
     } in
     let* (ctx', func) = gen_gc_function ctx_with_idx fd in
 
-    let export_names =
+    (* Export function if marked `pub` OR if its name matches a reserved
+       game-loop hook (preserved for backward compatibility, mirroring
+       codegen.ml). *)
+    let game_hook_names =
       ["main"; "init_state"; "step_state"; "get_state"; "mission_active"]
     in
+    let is_pub = (fd.fd_vis = Ast.Public) in
+    let is_game_hook = List.mem fd.fd_name.name game_hook_names in
     let new_exports =
-      if List.mem fd.fd_name.name export_names then
+      if is_pub || is_game_hook then
         [{ ge_name = fd.fd_name.name; ge_desc = GcExportFunc func_idx }]
       else []
     in