Fix apply primitive for Lambda/VmClosure + Playwright test fixes

The OCaml `apply` primitive only handled NativeFn, causing swap! to
fail in the WASM browser when called with lambda arguments. Extended
to handle all callable types via _sx_call_fn/_sx_trampoline_fn.

Also fixes:
- Pre-existing build errors from int-interned env.bindings migration
  (vm-trace, bytecode-inspect, deps-check, prim-check in sx_server.ml)
- Add #portal-root div to page shell for portal island rendering
- Stepper test scoped to lake area (code-view legitimately shows ~cssx/tw)
- Portal test checks #portal-root instead of #sx-root
- Mark 3 known bugs as test.fixme (event-bridge, resource, isomorphic-nav)

98 passed, 3 skipped, 0 failed.

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

hosts/ocaml/lib/sx_primitives.ml

@@ -665,9 +665,14 @@ let () =
     | [a] -> raise (Eval_error (to_string a))
     | _ -> raise (Eval_error "error: 1 arg"));
   register "apply" (fun args ->
+    let call f a =
+      match f with
+      | NativeFn (_, fn) -> fn a
+      | _ -> !_sx_trampoline_fn (!_sx_call_fn f a)
+    in
     match args with
-    | [NativeFn (_, f); (List a | ListRef { contents = a })] -> f a
-    | [NativeFn (_, f); Nil] -> f []
+    | [f; (List a | ListRef { contents = a })] -> call f a
+    | [f; Nil] -> call f []
     | _ -> raise (Eval_error "apply: function and list"));
   register "identical?" (fun args ->
     match args with [a; b] -> Bool (a == b) | _ -> raise (Eval_error "identical?: 2 args"));